It's bad PR with your core demographic.
There was no malicious intent from those comments - and he's done you a favour.
If his account doesn't get reinstated - Github has become something I didn't think it would whilst the founders were still in the business.
(Note: as far as your enterprise or big-corp clients, you probably did the right thing, because that is what they would have done and that is what they expected. So if they are the clients who put bread on your table, then you have acted correctly)
What I think you could have done better (and I speak as a developer not a corporate client): issue a public note saying something to the effect of "Thanks for finding this out, maybe you'd like to interview with us. But please, everyone, do not do it this way, this is against TOS and most likely illegal. Here is is the email where to report these things and we will make sure to give you full credit after we fix the problem".
Did github run over your dog or something?