I think the current consensus on the matter is to judge historical figures based on how they compare to their contemporary peers. This is generally considered to be the fairest form of judgement. A lot of people instinctively assume that morals and ethics are universal and can be transposed through time. It's hard for people to imagine the mental world of the past, wherein things such as racism are widely considered acceptable or wherein such concepts don't even exist yet. But it would be unfair to judge a historical figure for essentially not being a step ahead of the curve, seeing as we're ultimately shaped by our environment. We don't judge a Bronze Age blacksmith for not applying modern metallurgic methods - and the same thing goes for mental concepts in the past.

But as it is with historians and historical theory, you'll find plenty of historians skirting this "rule" by simply specifically mentioning something along the lines of "By today's standards, so and so held what would now be considered racist beliefs."

What's also important to note, however, is that moral judgements will happen. It's inevitable, much in the way that it's impossible for any historian to be free of bias or to be truly neutral. Your morals are part of how you view the world and it will effect how you interpret events, which emphasis you put in your work, and so on. A lot of historical methodology focuses on minimising the impact of this, but that's not so much a dam as it is a fishing net.

I find that the statement about withholding moral judgement is one that's made primarily in conversation with non-historians. In a conversation between historians, a lot of this theoretical stuff is unspoken, yet is assumed to be known by both parties. So while a lot of historians will still avoid making outright moral judgements when talking to each other, this is more because a level of nuance is expected than out of methodological zeal. When talking to non-historians, however, refusing to administer moral judgements becomes a useful tool. You can't go about explaining the basics of historical methodology to everyone you meet, go through the history of ideas in every debate - or simply give non-historians the necessary background to give them an accurate answer that they'll also understand the nuances of.

This sounds a bit patronising, but questions like the ones you mention in the OP put historians in an awkward position. You're asking them to use their expertise to answer a question - but the question itself ultimately shows (entirely understandably) a lack of methodological knowledge. Which leaves the historians with few options. They can either go on a lecture about historical methodology and how it's applied in this case - which can be too hard to understand when casually thrown around like that, which can be misinterpreted as an unwillingness to answer the question, which can be misinterpreted as a form of apologism, and so on. Or they can throw out the old canard of 'no moral judgements,' which still requires some explaining but at least shifts any blame/ire away from the individual historian to historical methodology.

Or they can simply say fuck it and give you the answer you want to hear. We can't always be dutiful historians, after all. Sometimes you just gotta say "fuck that Hitler guy. dude was a dick." without even considering the dickishness-levels of his historical peers.

You may find these threads on presentism and morality interesting.

The first contains some excellent comments by u/Alriclofgar and u/CommodoreCoCo, and the second contains some follow-up remarks by the same users, among others. (including myself, but I'm mostly just quoting others.)

The subject is slightly different, but the discussion focusses on the question of moral judgements to a large extent.

In general, I'd argue that moral judgements are not only inevitable, but aren't really a bad thing in the first place. Historians are people who'll have opinions. Judging people "by the standards of their times" as u/baronzaterdag advocates can indeed be a helpful approach as well, but it's not exactly straightforward either: who's standards do you use? The conqueror, or the conquered? The rich landowner's or his tenants'? The husband's or his wife's? Who's standards we can use depends heavily on the sources we have, and often we'll find one party or the other wrote all of them. Generally, the best a historian can do is to make sure to clearly explain these weaknesses and limitations, as well as his own biases and judgements, so the reader won't be misguided or mislead.

The bigger issue is that moral judgement should not get in the way of understanding. Asking "was slavery bad?" is a fairly trivial question, and answering it in the positive won't really further our understanding of history. Asking "Why did the trans-Atlantic slave-trade occur, how did the people perpetrating it justify it, and how did the people targetted by it react?" will teach us much more.

In the end, I'd summarise it as: A historian is allowed to make moral judgements. However, it is not the point of his job.

Historians use a process when we write, and there are some points at the process when moral judgment should be withheld, and others at which it can be (in my opinion) appropriate and even necessary for a historian to allow moral judgment to enter into our writings.

History is more of a method than a final product. The books you find on the shelves are products of historical labor, not history themselves (we use the term 'historiography' -- historical writing -- to describe finished books). History itself means 'inquiry,' and it's a set of critical methods for asking questions about evidence from the past to transform that evidence into meaningful stories that benefit our understanding in the present. History is a form of skepticism, investigation, and creative writing. When and how we allow our present day morality to influence this questioning process depends on what point in the process we're talking about, and the kind of historiography we're trying to write.

Historians begin by defining question that we're interested in answering. In my own research, the question is 'why were people in 6th century England buried with spears in their graves?' This question is not especially moral, on its face, but other questions might be informed by historians' moral concerns. The question, 'Why did Turkey slaughter Armenians in the genocide 100 years ago?' might very well come from a historian's personal horror and confusion that people could do something like that to each other. Similarly, 'How did conditions in early 19th century English factories change family structures' might also come from a set of personal moral prejudices about the good or evil of industrialization. This is, I would argue, a good thing -- it's important that historians study topics we find personally important and meaningful. My own research, in fact, does come from a place of moral value as well; the question of 'why bury' is caught up in my own concerns with how modern day society treats weapons and material things, and I hope, by studying this question in the past, to gain better understanding of why we make the choices we do in the present about valuing and disrespecting different parts of the material world around us now.

The next step of historians' work is to gather evidence, and here is the point where we have to set our personal values aside. 'Evidence' is a slippery thing, because there's a fair bit of subjectivity that goes into defining it. Some things like government tax records are pretty clearly evidence to anyone you ask, but other things -- personal diaries, artistic sketches, piles of trash (archaeologically excavated), or annual layers of pollen in the soil might not look like evidence to everyone. They can be evidence, however, if we keep an open mind and inquire broadly into the past. Historians widely agree that we must set aside our modern pre-occupations at this point in order to understand, as objectively as we are able, as much of the evidence as we can. Of course, no human can be actually, truly objective -- but by getting multiple perspectives, and examining things from as many sides as we are able, we can work to limit our subjectivity. Having a strong moral agenda, at this point, can blind us or lead us to rush past important different perspectives, so we must be careful to keep an open mind.

This open mind remains important as we begin to analyze our evidence. If we read everything from the perspective that Hitler was an evil man, it will be very difficult to understand his humanity, and we risk missing the 'banality of evil,' that is the fact that Nazis were real people like us, not unhuman monsters. Can we ever really understand what they did if we don't allow ourselves to recognize their humanity? (no.)

As we weight the evidence, however, our own voice starts to come back. We notice patterns, and these patterns eventually coalesce into the arguments that we write in our contributions to the historiography. Here, I would argue, it is not only appropriate, but often necessary for us to reintroduce our personal moral considerations. Why? First, because our morality will influence what we write whether or not we admit it, and it's better to be honest and upfront about the fact that no human can be truly objective. I mean more than this, though, because I don't actually think that the way in which our morality influences our writing is a bad thing. That's because, second, the goal of history is not to reproduce a perfect, objective, dispassionate analysis of the past. History is always going to be a story told to make sense of surviving traces or evidence from the past, and as such it must have a storyteller. This isn't a limitation of the discipline: it's the heart of what we do. And good stories have a point -- they're more than a gripping yarn. Good stories teach lessons about things that matter. Third, history is a powerful tool to challenge the world we live in today, and we miss a valuable opportunity if we refuse to use the past to question moral concerns in the present.

Most importantly, however, I do not believe that one can write honest history if one insists on putting neutrality above all else. In an unbiased analysis, Lovecraft was a racist. He would wear that label proudly, I think (our resident lovecraft expert can correct me if I'm wrong!), as scientific racism was a popular and respected position at the time when he was writing, and it's clearly an important part of how he viewed the world from his works. If we dance around Lovecraft's racism, we're not actually being fair to him as a writer. We're putting political correctness ahead of honesty: because, honestly, he was absolutely a racist, and many of his ideas are pretty morally repugnant to modern readers. We should, as I said above, try to understand Lovecraft on his own terms, as a human, and not treat him like some sort of monster. It's also very important to understand that morality changes through time, and to evaluate how people in the past fit into their own moral systems (this is how we question and better understand our own morality). But at the end of the day, we should be honest about what we find. The same goes for Nazis -- they were people like you and me, but no honest evaluation should find their actions morally neutral. Honesty demands, in the end, that our analysis contain a moral judgment alongside our other evaluations.

Not all historians agree on this. Some would say that we should carry our objectivity to the end. Personally, I think there are problems with that attitude, and I think that history is at its best when it discusses evidence with balanced fairness, and yet offers an analysis in the end that speaks on a moral as well as evidentiary level. Anything less is missing out on the opportunities for honest inquiry in all aspects of the past, including its moral dimensions.