I was planning a post with this title, but after some preliminary discussion, a commenter on Twitter pointed me to this piece by David Armitage, which not only has the title I planned to use, but a much more complete and nuanced presentation of the argument, as you might expect from the chair of the Harvard history department.
I won’t recapitulate his points, except to make an observation about disciplinary differences. The dominant view in history described by Armitage as “professional creed: the commitment to separate the concerns of the present from the scientific treatment of the past” is identical, with a slight change in terminology, to the central claim of “value-free economics”, that it is possible to separate the positive science of economics, from the normative question of what economic choices should be made. 
What’s striking here is that the idea of “value free” economics has been the subject of severe criticism for decades, starting in the 1950s with Gunnar Myrdal . Hardly anyone now puts forward claims of this kind in the strong version presented most notably by Milton Friedman. This view is routinely denounced as a residue of “logical positivism”, an pejorative with much the same valence as “Whig history”, except for a reversal of sign.
Armitage’s defense of presentism runs along very similar lines to the critiques of value free economics. Most notably, he observes
can we plausibly deny that we choose our subjects according to our own present concerns and then bring our immediate analytical frameworks to bear upon them?
Referring to history specifically, he says
only history—again, only our individual experiences and that collective record of the human past in all its forms, from the cultural to the cosmic—can supply the information and the imagination to shape our choices, in the present, among multiple potential paths into the future. If historians too freely use presentism as a slur or as a taboo, then we may be guilty of depriving our readers, and indeed ourselves, of one valuable resource for promoting human flourishing: history.
One point Armitage doesn’t discuss but which seems critical to me is that, if historians reject presentism, they seem to be disqualified, at least qua historians, from saying anything useful about the present. It’s impossible, for example, to talk about (or even to name) last year’s insurrection without bringing in terms and ideas that are value-laden.
But, looking backwards, when does the present stop and the past begin? Should Thatcher and Reagan be regarded as people of their times, exempt from critical judgement? What about their opponents and supporters who are still living? Should historians treat their (or rather, our, since I’m among the critics) actions in the 1980s as objects of study, disregarding our own belief that our concerns then are just as valid now.
Similarly, if it’s appropriate to condemn Donald Trump’s racism now, does it make sense to view the same racism, as expressed by Trump in the 1960s, as a morally neutral product of the times?
And given the fact that generations overlap, there’s no obvious end to this. How should we think about the relationship between Donald Trump and Roy Cohn, or between Cohn and Joe McCarthy?
None of this is to say that people should be judged according to our own local and temporal standards, without reference to their own circumstances. The racism of a privileged New Yorker like Trump says a lot more about him personally than the same attitudes held by a poorly educated white farm worker in Mississippi. Similarly, there’s a big difference between attitudes expressed at a time when nearly everyone accepted them to the same attitudes expressed when they are widely condemned.
But the idea of a value-free social science has been tested to destruction in fields like economics. It is no more defensible in history.
fn1. I didn’t mention this in my tweet, which focused on the contrast between economics and history
fn2. There’s a similar debate in political science, but I don’t think the “value free” approach ever gained the same dominance as it had economics
fn3. This was only 20 years after Butterfield’s denunciation of “Whig history”, which seems to have carried all before it among historians