Spam flags and offensive flags are strong weapons: they automatically decrease the points of a post, and with enough flags the post is deleted.
On MathOverflow, it is a custom to flag crank posts (for example, "This entire field is rubbish and worthless") as spam. While math.SE should be somewhat more tolerant of people posting borderline content, people calling certain fields rubbish is not something I'd like to see on math.SE, and to some extent I find it to be offensive. (Especially if things are meant seriously.)
But I do recall a discussion saying that spam flags should be reserved for actual spam. So, what's offensive? The very title of the flag says "it is not welcome in our community".
I recently raised an offensive flag against such a post. And it was quickly rejected by a moderator, leading me to ask two questions:
Do 10k users see offensive and spam flags? Or are they only shown to the moderators? If the former is true, then declining the flag was against the idea of letting the community moderate itself.
Do we want to have such community norms, similar to the one on MO which supports flagging crankish posts as spam/offensive? If so, what would be a typical case where one should consider raising such flag?