I fear that a majority of commenters have decided that they know what you have said without reading it, and are responding to their own ideas. A pity! You make some interesting points.

It's good to situate the current (anti-)DEI rhetoric within the longer-term trends on the right and the left.

The American left has been developing a deepening fascination with moral purity, while the American right has been leaning into the organizating power of reactionary reflexes (to call it reactionary thinking would be too generous).

This has led to successive waves of superficially good-sounding ideas with a fair bit of judgmental holier-than-thou nonsense from the left, which the right has seized upon, mischaracterized further, and used as a rallying cry.

You can see the same pattern, albeit played in slow motion, with "political correctness" in the late 80s and early 90s: the left introduced a variety of ideas that were supposed to be morally superior to the status quo, but there was very little tolerance for careful appraisal of which ones were good all the way through, which were good in conception but weren't being implemented well, and which were ill-conceived. This left parts of the project vulnerable to legitimate mockery from the right, which the right was quick to extend to mockery of the entire idea (including the parts which were desperately overdue corrections to barbaric historical norms).

DEI is only the latest in the series--they've been coming fast and furious in the past decade, going through social justice (warriors), critical race theory, woke/"wokeism", and DEI in rapid sequence.

It's a remake of the same script over and over again.

Jumping in at the point where the right is relentlessly mocking something sans evidence gives only a part of the picture. They do do this, in spades, and it's invalid, just as you describe. But it usually doesn't come out of nowhere; it's more effective when the left has allowed bad ideas to fester because the appearance of being morally superior is valued far more greatly than actually doing good.

The actual DEI efforts--at companies, universities, and so on--have fallen afoul of this. The reactionary wing of the right has gleefully taken this as an invitation to throw the baby out with the bathwater, and criticize anything and everything as DEI (where DEI = bad), sans evidence (and sometimes blatantly in contradiction to the obvious).

Alas, as you can see from the comments here, it is depressingly difficult to keep the baby and throw the bathwater away.