Every action is technically a "product of its time." There is no way to not be, to some degree, a product of your time. That's the thing about context: you cannot escape it, whether you want to or not! But context is not a railway you are bolted to — every context, now as much as in the past, contains lots of people, lots of places, lots of possible options and opinions. These are two fundamental beliefs of historians (and "historicism"): everything is by definition a part of its context, but there is also always contingency, i.e., forces that allow for choice (and modification of context).

The question is, really, how do you judge the actions of the past? Usually the bar is something like this: if nobody thought something was a problem in the past, then you shouldn't judge people too harshly by acting in accord with the moral standards of their time. This allows us to give ourselves some leeway today — if, say, in 100 years it is decided that owning pets is immoral and terrible, we wouldn't want anyone in the future to judge us for not realizing that. Of course, there are some people who think owning pets is immoral — they are pretty fringe, but they exist. How do we decide how to deal with that, then? There really is no cut-and-dry answer, and anyone who wants to give you one usually has a point they are trying to make in their favor.

When I am trying to understand how an action was judged at the time, I look for contemporary sources that give a range of views. Was Columbus viewed harshly in his day? I don't know about Columbus specifically, but there were many voices who thought that the Spanish approach to colonization (enslave the natives in the name of religion and commerce, work them to death in many cases) was particularly barbaric, at least by the 16th century. Perhaps someone else can comment on that aspect of the question.

To give an example from a time period I know well, though: towards the end of World War II, the United States began a program of systemic bombing of cities in Japan. Not just Hiroshima and Nagasaki, but 67 other cities were systematically burnt out and destroyed using firebombing. Hundreds of thousands of civilians were massacred in this way. How should we judge such a thing? A common response is to say, this was common for its era. Which is true to a degree: all sides engaged in democidal tendencies during the war, and the deliberate area-bombing of cities had been inaugurated earlier in Europe. Which can make it easy for some to say, there is no moral judgment in retrospect — it was just how people thought about war at the time.

On the other hand, though, there were many non-fringe figures who thought this was a problem. The US Secretary of War, Henry Stimson, considered such bombing to be a true moral hazard, and worried openly (to the President, no less) that the US might "get the reputation of outdoing Hitler in atrocities." So that's a pretty strong moral judgment, passed by someone who knew how war worked, and was part of the central command structure. (A longer discussion might include why the Secretary of War had to make arguments like this to the President — the military was very much calling the shots on this matter, not the civilian Executive branch.) With that knowledge, I think it's possible to say, "not everyone thought this was morally sound," and that opens up just enough uncertainty about the outcome to pose it as a moral question and not a moral fait accompli. Other sources useful in discussions of that event include US public opinion polls, which were mostly, but not exclusively, in favor of such tactics.

But entirely separately between whether we feel we ought to "judge" or not (or to what degree), we might consider why we are asking the question. Does Columbus care what we think about him? He is long dead, so I think not. But if the question is, "should we have a national holiday that valorizes a man who did many things we would not endorse today?" — that's an entirely separate question. Because it's not a question about the past, it's a question about today. We are allowed to change our mind about what behavior we want to laud today with national holidays and parades and pats on the back. We are not bound to a past morality. We don't have to name things after slaveowners or put people who commit massacres and human rights violations on our currency. We get to make the choices about our present, and the past cannot bind us to such things. That does not mean we should not discuss the past (obviously!), or take a nuanced view of it.