Problem is, that's just the sort of thing these people are resorting to--ANYTHING they can to barb your psychological well being. They might be kinda nuts, that doesn't mean they are necessarily stupid. Course that doesn't mean they are the only ones that can "lose it" either.
Then you also have people who make threats or something to try to rattle sabers or whatever charade and try to intimidate you into doing what they want.
The real danger are those who don't want your attention because they actually mean to do you harm; these are more dangerous than anyone else. Then there are masterminds doing both.
Of minor relevance you can tell a lot by someone's body language and demeanor in person if you know what to look for.
Point being is gauging the threat level: you can safely ignore many extremists, but that doesn't mean there aren't still people among them who will do something waiting for you to turn a blind eye.