I think you argued the wrong way. The maintainer states it's skill not political views that give merit. If github hired Coraline for her political views, then github stated it's political views not skills that give merit.
> Either they have an obligation to be politically correct as a VC-funded startup that needs to ensure its public face is immaculate
Immaculate? There's no black and white here.
> or Coraline is a fantastic Ruby developer who is good at building community management tools and her politics are irrelevant.
Yes but Coraline will never be satisfied with just being a fantastic ruby developer. It was pretty clear from her comments she cares more (or at least as much) about people than software.