It's a difficult situation to explain, and it will be even harder to judge.
What seems to be true is that they had a hold on him. They seemed to abuse his mental weaknesses, and regularly made themselves look like benefactor for "saving him from himself" and making him earn a lot of money.
Sure he could have technically walked out any day, but when you're under the influence of manipulative "friends", I'm not sure it's that easy.
Bear in mind that I'm not stating 100% proven facts.
It depends. Do you consider Twitch's moderation to be to extreme? They definitely wouldn't have let this slide. I'm pretty sure they used to stream on twitch and got banned there.
Kick is currently very lax when it comes to moderation (it's their niche, their way of existing even with Twitch's dominance), and I don't think banning channels promoting group punching a dude would be a bad thing to censor.