It’s not his belief that hurts us. It’s that he actively donated to a cause that directly negatively affected us, personally. It’s not abstract. It’s not a witch hunt. He’s certainly allowed to have his opinion, of course, but I’m allowed to judge his actions of supporting the cause financially.
Actions have consequences."
There you go, sums it up right there. Some past actions are hard to overlook when you're personally affected by it. However you view the news of Brendan Eich's new CEO position and people's opinions of that, you can't ignore the human element of his insignificant (financially) but significant (philosophically) prop 8 contribution and how people take it personally.
Edit: Adding onto my thought of how I view the human element in this story: we all try to be rational, but I bet you everyone of us throw that away for a gut feeling we have of someone. If you don't like someone, no amount of reason will make that go away. That feeling spreads to what they're associated with. In retrospect, we reason our gut feeling and we either turn out right or wrong. I understand hcatlin's decision in that sense since I have felt that way before.