You talk about Elon and Twitter users like some specific people talk about Soros and the Jews. Both are a form of blaming groups of people for some random, different person deeds. Not acceptable.
Just from the wording my quick judgment is that ADL is the bully here. You can't walk around calling people "unrepentant bigots", and doing that in public is IMHO indeed defamation, which Musk is suing for.