Why should this warrant a ban though? It was his GitHub repo and as far as I know you are allowed to put anything you want in there as long as it's not a breach of copyright, illegal or inappropriate.
Exactly, GitHub repo should be his free speech.
FWIW, it looks like this is about the NPM account, not the GitHub account.
he can use his own hit repository for that. git is distributed.
I think the reasoning is that he betrayed his responsibility as he was a part of the Open Source supply chain, which he started using for other than its advertised purpose.
Mistake of judgement sure, programming mistake not so much.