Have you considered the possibility that both parties are in the wrong? That Horvath does have something of a point, but she's massively overblown her experiences and read the wrong meaning into things?
Life is stickier than tabloids lead you to believe, and in such a case as I've suggested, it's not hard to see the founders talking about how 'bob' should take a brief sabbatical while the Internet Hate Machine looks for another target. The other founders might love 'bob' and want to spare him from internet fury. Or they might loathe him and were looking for a way to put him in his place. Or they might be taking a pragmatic PR-smart move. Or 'bob' might have said "I was looking to take leave and go to Europe for a holiday, this would be a good time, eh?". Or a dozen other situations. We just don't know.
And that's just fire-fighting - if you want Github to do a meaningful investigation, then you need to have the investigators being as dispassionate as possible, rather than doing it while fending off the hordes at the gate. And since a founder is involved, the investigators pretty much have to be the other founders. And that meaningful investigation includes talking to staff outside of the bubble of hysteria that's currently going on. And that meaningful investigation may indeed largely exonerate Github.
The thing is that you don't have enough information to pre-convict the way you have.
And, frankly, on a personal note: fuck this automatic calling for the sacking of someone when thing go awry. It's truly fucked up. Re-evaluate? No. Retrain? No. Reassign? No. "Someone has to suffer" for the mob's one-eyed rage. Fuck that shit. Sometimes a sacking is the appropriate course of action, but that's not for the mob to decide, because the mob doesn't have anything like close access to the story.