Wasn't he basically just saying that these kinds of statements radically lower his epistemic confidence in empirical claims the movement makes which are politically convenient?

Well, there's the connotative issue involved. But my point is that he seems to be making a strange adjustment here: Making a radical adjustment to one group when it should apply to all political groups. Moreover, the comment struck me (and it is possible that I've misinterpreted it here) as essentially dismissing any claims made rather than doing what one should actually do in such contexts- carefully examine the claims, and look for omitted evidence.