Blocking him is the best thing you can do. He is really a known troll, who has already been banned in other communities. He spreads dangerous misinformation, as you can see, and accuses people of being racist without any proof. Furthermore, he basically just a bully who like to harass other people in every discussion he has. As @ArtilectZed@lemmy.ml said, don't feed the troll is the best approach.