If he's butthurt over such a tiny change (one that is entirely legitimate, all things considered) in documentation, they're right for calling him an asshole.
Seriously, go look at the diff that he had such an issue with:
https://github.com/alex/libuv/commit/1ff9d18d398fb9f35b72fa0...
He could have just smooshed the big green button and scored one for the "not pointlessly defaulting to masculine terms" team, but instead he had to turn it into an "omfg no this is stupid" debate.
Inequality doesn't change by embracing the status quo simply because that's how we've always done things. As much as Joyent look like turds here, they did the right thing.
If he'd worked for me, I'd have fired him for such assholery too. We're talking about a one-line documentation change of "him" to "they", for fuck's sake.