Eich might have defenses, but Philip's writing here is extremely weak.
1. A lot of people aren't viewing it as a "political" view like they would taxation or immigration. They see it as straightforward human rights. Just like we'd expect backlash against someone against "interracial" marriage. Even if we're saving those cross-race couples from expensive litigation!
2. He spoke about his views and got all cagey. If it was an accidental donation for a friend, he could simply admit so. Instead he refuses to elaborate. Perhaps he hates Prop8 and just wanted to see where this would end up. Or perhaps he is against all marriages in their current construct. If such things were true, then he could state his proper views and it'd be finished and mostly blown over.
3. It still might be an overall loss as civil rights will almost certainly end up in the right place. But it's not clear that an open web, for as much as Mozilla is fighting for that, will happen. I'd accept a hand from the most evil person in the world if my alternative was drowning.