Lemmy is developed by two (2) people and asking for one of them to leave is effectively just killing the project. If you don't like it, you can move to an alternative such as PieFed.
Personally, I can't make myself care about this too much. It's a doshit take (somewhat understandable considering the guy's background), but it was publicised over a year ago, he hasn't said this sort of crap since then, and Dessalines' whiteknighting for Russia is IMO way more of an issue morally and politically. But at the end of the day the question is whether Lemmy works fine for you or not and whether the admins' opinions harm your experience. I don't think they do, Dessalines bans criticism on his turf but it's just a handful of communities, while the devs are still providing the infrastructure for diametrically opposed views and communities.