Especially when he has clearly proven on his website that he has highly nuanced takes on various other, less controversial, topics. It reminds me of people trying to shame Scott Alexander for daring to step a little outside the Overton window himself.
It may be rational of you to interpolate the quality of one facet of someone’s behavior from other facets, or to interpolate from one social controversy to another, but it’s certainly not adversarially robust. You can’t reasonably expect people not to focus on his narrower behavior in one area.
I can buy that often people are specifically opposed to racist bigots, i.e. people who are unreasonably attached to the idea of racial group differences. The essence of being unreasonable is to not be able to be reasoned with, and being reasoned with often involves presenting specific cruxes for discussion. It seems to me that Cremieux tends to do so, and so he is not a racist bigot.
I think part of what can get him persecuted for being a racist bigot is that a lot of rationalists follow him and more-or-less endorse (or at least defend) racist stuff without being willing to present cruxes, i.e. his fans are racist bigots. It’s hard for people to distinguish a writer from their fans, and I suspect this might be best addressed by writers being more internally oriented towards their fans rather than outwards oriented.