Because this isn't just a private matter. Peter is very vocal about his vision of society - in which tech plays a big place - and this donation definitely gives some interesting color to that vision.

I would say so if he's a YC advisor. He doesn't have to justify his actions but it would be interesting to understand or at least try to understand his point of view. My guess is it has to do with taxes.

What people choose to do with their person wealth is important, when they use their wealth to influence elections.