I think the "fun" comes from the sport of seeing how far they can go in provoking other people by taking extreme behaviors and speaking about them in a casual,

I think the "fun" comes from the sport of seeing how far they can go in provoking other people by taking extreme behaviors and speaking about them in a casual, normalizing tone. Which, needless to say, is childish, wasteful of everyone's time on account of its disingenuousness, and doesn't reflect well on one's personal character or maturity.