Legally they might be in the right, but punishing victims of social engineering further doesn't seem like a fair or smart business decision.

Suppose there is a service which allows you to watch free porn videos as long as you hand over permissions to star a bunch of repos using your account. Clearly, the service is abusive and should be banned. But isn't it also quite fair for Github to penalize the users? They knew they were handing over something of value when they authorized the access. Either they chose to exchange their genuine 'Github clout' for something they wanted, or their accounts are spammy in the first place (for example, if they created an account solely to access that service).