My son posted an historian's tweet thread accusing other historians of a consistent set of assumptions and biases which prevent full inquiry. He made a decent, though not overwhelming case that such a thing is possible, and does in fact happen.
The best evidence for his point comes from the historians refuting him, however. They use the "No True Scotsman" argument; they ask for examples but ignore the ones given; they are merely insulting - name calling without providing evidence that he "simply does not understand what professional historians do;" they assert that their political opinions do not bias their conclusions so much as their political opinions derive from their superior knowledge. I have mentioned before that one mark of a person having no insight is a 100%-0% characterisation. Not one of the critics said "I see what you are saying, and it does sometimes occur, though not to the extent you accuse." They all said "Nope. Not never. Historians never do this. Not us. You're ignorant." It's one of the primary markers of fools, to not allow that even 1% of a criticism is fair.
I say the shaft went home.
Beginning before my career started, but still happening when first I started in psychology, the entire field was overthrown as Freud (who set us back a century) was gradually discarded. It is now being overthrown again because of replication crisis. As the Freudians were going down, they made the same arguments dismissing their critics that the historians are making now. As the replication crisis sends more sacred cows to the slaughter, this current generation is acting the same way. "Nope. Not us. Impossible. You are ignorant people who just don't understand." Sociology and Anthropology are showing similar fragility, as clearly politically-biased trends from 50 years ago are being overthrown by hard data: DNA, archaeology. (See, for example, Lawrence Keeley's War Before Civilization.)
Historical linguists sneered at Greenberg's division of New World languages into only three groups, from identified migrations, but DNA is now dividing the tribes into just about exactly those three strands. You'd think they would have learned their lesson after rejecting, then accepting, his simplification of the African languages. But he'd made mistakes, you see, and so couldn't possibly be right.
The protest from the professionals is that they interrogate themselves and each other quite severely on every topic, considering what assumptions and choices are being made right at the outset. I don't doubt this in the slightest. From what little I can hear over the transom, this is indeed what they do, and I think it is very healthy. Asking whether this is from the perspective of the underclass, middle, or overclass is important; stepping back and considering how this played out differently for men and for women is valuable; examining whether the source material comes directly or indirectly from those inside, from allies, from competitors, from enemies, and at how much distance in time and space is basic. Yet this must also teach that the variety of perspectives can be multiplied endlessly. To then turn and say "We haven't missed anything important" is almost a self-accusation of having missed something important at that point. You are the very ones who told us to not trust even our own thoughts. It rather looks like you want us to question our assumptions, while you flood the market by questioning 90% of your assumptions intensely, always leaving the same 10% out.
I know only a bit about how PhD theses in history proceed, yet it does seem that much emphasis is put on the technical craft (which is fine), plus engaging in the interrogation according to the current fashion. I have had one tell me that he could not do the thesis he really wanted to, because in this climate one has to check one of a limited number of boxes (he did not say "PC," but that is what he described) to even get it approved. This creates an illusion of reasonableness, of fairness, of attempted objectivity that is actually just a cargo cult response.
Are they skilled technicians who are told they are philosophers?