I almost always avoid making those kinds of comments when I’m moderating. I made an exception here because I felt the characterization was correct, and even Chief Pedant wasn’t arguing with it, and because if I’d made no acknowledgment of the content of the posts it would have lead to a longer argument about the rules.
brickbacon was asking, in essence, if it’s okay to call a poster a racist in Great Debates if it’s true, or if the poster acknowledges it. I think tomndebb and I agree that in both cases, it isn’t because it’s still a personal remark.
I think your understanding of the group insults idea is correct. But vaguely saying “many” people are racists is too vague to be a personal insult in my opinion.