The problem with arguments is that everyone who has a view (i.e., everyone) considers themselves an expert. Stanley Fish  lends credence to this view. In a recent op-ed on Historians Against Trump, he writes:
But there’s very little acknowledgment of limitations and subjectivity in what follows, only a rehearsal of the now standard criticisms of Mr. Trump, offered not as political opinions, which they surely are, but as indisputable, impartially arrived at truths: “Donald Trump’s presidential campaign is a campaign of violence: violence against individuals and groups; against memory and accountability, against historical analysis and fact.†How’s that for cool, temperate and disinterested analysis?
Now, don’t get me wrong. I’m not saying that this view of Mr. Trump is incorrect; nor am I saying that it is on target: only that it is a view, like anyone else’s. By dressing up their obviously partisan views as “the lessons of history,†the signatories to the letter present themselves as the impersonal transmitters of a truth that just happens to flow through them. In fact they are merely people with history degrees, which means that they have read certain books, taken and taught certain courses and written scholarly essays, often on topics of interest only to other practitioners in the field.
This strikes me as very confused. In the first place, what on earth are “political opinions”? Are the on par with opinions about matters of taste? (pizza is great!) If so, then indeed, maybe Fish is right. But I doubt this is what he means. Political opinions, after all, include all sorts of things that are fact-based. One example would be: “we should do this because it worked in the past.” The test of the acceptability of this opinion would be whether this indeed worked well in the past. That’s a factual question. Historians deal, allegedly, with such past-tense factual questions. In makes perfect sense that they weigh in.
On another level. Fish has hugely exaggerated the force of the argument from expert opinion (of which this is an example). Experts, which historians surely are at some level, are called upon (by reasonable people) to help with questions that fall within their expertise. For this reason, we call upon doctors to comment on political matters when those have bearing. We can call upon historians to answer questions about history. It does not mean, nor would anyone anywhere suggest, that such opinions are the same thing as truth itself than cannot be objected to.
Naturally, all of this is just my opinion.