Most likely a mixture of guilt and, in all seriousness mental illness.
A lot of these guys are in the artistic side of things, comedians, artists, film makers.
The arts has a high level of mental illness driving the creativity.
When someone who's already barely functioning and using whatever industry they've mastered as a crutch suddenly find themselves being ostracized by that crutch, even if its short term, its going to get ugly for them and they react like.. well like this.
It doesnt matter if the most logical thing to do is to keep quietly moving forward no matter how much truth there is in the allegations, they'll spiral out at the slightest tug because the crutch is all they have.
John K in particular has serious issues, mainly with his own father, a bunch of people suddenly turning and hating him has probably warped him back to that same helpless feelings he's always struggled with and now he's desperately trying to win back the affection he's filled the hole with.