You wouldn't be responsible, of course. The idea is preposterous. He is an adult and should be responsible for his actions, the same as any one of us.
But here's something to ponder: if he doesn't have any idea of what he is doing as you seem to imply, how can he change? How would he know what to change? I've thought for a long time that TCO has little or no control over his meltdowns, and that quite a few of us see them coming long before he does. Certainly PPK did, this time.
And quite a few know perfectly well how to use them and to provoke him further. But does fueling his meltdowns help him or anyone else? I doubt it.
Mind, I'm not defending what he said about you or your family, just as I'd not defend what you said about him or his family, I'm merely asking you because while you're angry, right now I consider you to be more rational than he is.
As his friend, I hope he can get help because he is hurt far more by his meltdowns than anyone else.
I do agree with almost everything you're saying, but it does totally miss the problem that I have with Steve.
I don't care about his meltdowns. I don't care that he has wished death on me and my family and threatened to beat me up. I don't care that he wants my dad to attack me, or that he thinks I'm the ugliest person in the world.
My problem is that he continually blames everyone else for everything that he does. Even after his meltdown, he is constantly looking to rewrite history to blame everyone else, and turn himself into the victim. Fuck, he's even tried to blame Schleed for this one. He will accept no responsibility for any of his actions. I hate people who blame everyone else for everything, and Steve is the worst person I have ever known for doing this.
He's not my friend. I really dislike him, and I have no interest in helping him, or even making anything easier for him. At least not until he accepts responsibility for his own actions and stops blaming others.
You are his friend. If you want to help him, then the best thing you could do would be to make him understand that he, and he alone is responsible for his actions. Make him understand that blaming others for his actions will only attract scorn.
Make him understand that it's better to fuck up, but to accept responsibility for that fuck up, than to attempt to divert the blame for his fuck up.
And please. Try and make him stop being such a crybaby.