Having personal beliefs is fine. Taking away the freedom of others is not. You don't have to back proposition 8 to believe homosexuality is immoral, just like you don't have to outlaw pork in order to keep kosher.
He supported a very mainstream position. Even if it is not mainstream on HN or in silicon valley or on tech news sites, it is mainstream when you look a little outside.
I oppose that position as I said above, but because it is held by about half of the population, we can't just refuse to work with anyone holding that position.
Well, over half of the population that voted had the same opinion. Voter turnout was around 60%, iirc. Additionally, even if 60% of people held the same views, it's still possible to choose not to work for them.