Depends on which subreddit and which flavor of groupthink. The behavior you say is upvoted is one I often see downvoted to oblivion on Reddit.
> but if someone calls them an asshole about it, they're flagged.
That's because name calling is against HN guidelines.
Just an aside since it's not clear: I think the asshole is the one using labels like "decel" (or even "MAGA" unless the person self describes). It's irrelevant if I agree with the rest of the comment.
It's OK to call people out for name calling while still agreeing with the rest. It's problematic to require one acknowledge the quality of the rest of the comment when calling them out on their name calling.
Put in a less twisted manner: If it's OK to address his comment sans the "decel", it should also be OK to address his use of "decel" without discussing the rest of the comment.