A few people commenting is not widespread support. I was at Mozilla at the time and I didn't get the impression that the views you linked were broadly representative.
And FWIW: I didn't personally feel the backlash at Brendan was appropriate, but given that it existed the outcome was probably unavoidable.
I say this as someone who, while living in Virgina and having never lived in California at the time prop 8 was on the ballot (I moved here a few years later), I donated to opposition to CA prop 8 and decided to not get married to my (opposite sex) partner out of solidarity with gay people who couldn't get married in our state.
I never felt that I should be or would be persecuted at Mozilla (which employed a lot of christians, and particularly Catholics), if it had become public that I funded opposition to prop 8. Nor, by the same token, did I think it was appropriate for Brendan to come under fire for funding support for it. I have sympathy for the theoretical argument that it might be difficult to work for someone with personal views incompatible with yours or your identity, but in practice Mozilla was an an extremely open and inclusive place that employed people of all kinds and treated them with respect. (In other words, a theoretical problem which wasn't in this instance a practical problem by any report I heard.)
Although I don't have any actual knowledge, if I had to speculate I would guess there were other Mozilla employees who supported prop 8 (many?). -- especially considering that prop 8 _passed_ with >52% support.
Even though I strongly disagreed with him on this subject (apparently! not that I'd have any way to know other than the media coverage of this), the incident made me feel slightly less safe and welcome there-- because clearly your lawful and constitutionally protected outside-of-work personal/political/religious views were potentially subject to scrutiny. Although not very much so, because it appeared clear to me that the events were primarily being driven by public noise, and not by some internal wrong-think witchhunt.
His views weren't the problem. His actions were. And not thinking his actions were discriminatory.
The CEO is the face of the company and oversees HR. Most people who objected to Eich being CEO didn't have a problem with him being CTO.
Believing different races shouldn't mix is legal. Just saying it in public will disqualify you from being CEO at most companies. Never mind funding a constitutional amendment.
