This is... a fundamental oversimplification at best. First of all, what's a neutral historian supposed to be? Why is supposed neutrality in opposition to "liberal" or "socialist"? Do conservative historians not count at all? How would someone not well versed in the scholarship be supposed to weigh the different viewpoints presented by these supposed socialist, liberal, and neutral authors?

The way most academic history operates is that if you read the introduction to a historical monograph, the author will set out to answer a specific question about a specific subject. In order to arrive at an answer to this question, they will also chose a certain methodology, which in turn will fit into a broader theoretical framework.

So, for example, a historian setting out to answer the question what the important factors of causing the French Revolution were might approach the topic from a marxian angle and focus strongly on the economic conditions of pre-Revolution France; they might approach the topic from a standpoint of intellectual history focusing strongly on the ideas of Enlightenment writers about society and the state and how they influenced the primary political actors of the Revolution; they might approach the subject with a "from below" methodology focusing on what immediate circumstances lead to French citizens taking part in the Revolution; they might approach the subject from a cultural history perspective and focus on how the social context change to influence the perception of French citizens of the world around them; and so on and so forth. Methodological choices are myriad as long as there are sources in their support (f.ex. you can only write a history from below if you have sources from below).

And the difficult thing to grasp is that when executed with sufficient primary source support, all these approaches are valid in the sense that nobody in the history of history has ever managed to write the definite book on any one subject that explains every aspect and stays uncontested or unchallenged forever. Human society is far too complex for one person to be able to sufficiently cover everything and explain everything. That's why history is a field of constant discussion, addition and revision; why we'll never be truly done researching the past; and why we will never achieve to intellectually grasp the final and absolute truth in an interpretation but can only every try and contribute to a deeper understanding of a subject and/or period without every being able to have fully uncovered it.

Of course, historians will always have discussion whether one particular methodology, theoretical framework, or interpretation resulting from that is valid, supported by sources or even the right way to approach a question in light of both sources and limitations of a certain methodology. The problem with that for the layperson is however that without a deeper expertise in both the subject in question and the methodology and theory in question, it can often be hard – if not outright impossible – to weigh these different interpretations against each other. Assuming you read both an economic-centered and idea-centered history of the French revolution where both authors claim greater explanatory potential by their chose methodology – how – without knowing the sources, without being familiar with the interpretative implications of both approaches – can a layperson truly decide which is the better approach to the topic in question?

Certainly, there are ways that can be easier, from looking at journal reviews to other methods of parsing out what the academic public at large thinks of various interpretations and their framework. But this is more complicated and more work than just reading three different books. And if you read one book by a socialist, one by a liberal, and one by a third historian about, say, the French revolution, there is also always the possibility that all three of them have important points by covering different aspects of an immensely complex subject.

To claim that one needs to read a book from one perspective, then one from another one and has arrived at "the truth" by deciding that it is somewhere in the middle between those two (or three) simply doesn't work. In light of the available sources, both might be "true" or one is indeed more suited to explaining the subject in question where f.ex. an economically centered approach might indeed work better at explaining industrialization than one that focuses on the Great Men of history, given all that we know by now about the complexities of society. Or where a cultural approach to the Lutheran Reformation might indeed hold greater explanatory potential than an economic centered one.

This is the reason why we want contributors to this sub contextualize their answers and be able to cite sources. It's also the reason why academic historians also include in their introductions a discussion of the available research done by other historians and make their argument why their question and approach is better suited than what has been done already. And it is also why gaining a PhD or equivalent expertise in a given historical era/subject takes most people about 10 years to achieve and never really stops.