There was a recent discussion about ElectronConf (organised by GitHub) that highlights this .
It doesn't have a culture so this is really inflammatory, and unnecessarily so. Or were you referring to GitHub the organization and not the set of people that use it?
They are also somewhat infamous for having hired one self-proclaimed "notorious SJW" who previously harassed a GitHub user for his contribution to some unrelated Twitter flamewar and later went on to work at GitHub on "community management and anti-harassment tools". Go figure.