I recently flagged as "rude or offensive" the comment
As the tone should suggest, he’s a crank. It’s a hysterical screed with a few nuggets of fact surrounded by a great deal of nonsense. E.g., he may find that set theory ‘doesn’t make sense’, but a great many of us have no trouble making sense of it. – Brian M. Scott
to the question
My complaint is very narrow: I am not arguing that the subject of the comment is right in his critique of infinite sets, only that the word "crank" is inappropriate in this context. In particular, none of the answers to the question provide evidence of crankdom, but rather disagreement over philosophy. If the comment had simply been
"He may find that set theory ‘doesn’t make sense’, but a great many of us have no trouble making sense of it."
I would have no objection.
I could also have flagged it as "not constructive/off topic" or as "too chatty". But to my mind it is the unwarranted rudeness that is the real problem here. More generally, I am quite upset that a productive mathematician is being called a crank. I don't know the subject of the comment personally, but I am familiar with his work and he is most definitely not a crank.
Comments like this reflect quite poorly on math.stackexchange and I hope not to see any more of them. What is the best way to encourage commenters to refrain from baseless accusations of crankdom? Is flagging the appropriate course of action?