I agree in general. So long as humans partake in decision-making, decisions will be made according to the minds involved.
I would worry about the possible impact of Brendan's personal beliefs if I thought that he truly has a heartfelt disdain for whole classes of people, but as far as I can tell, he doesn't.
The question of whether to support gay marriage doesn't always reduce to bigotry and homophobia. In Brendan's case, although no one seems to know, I think it comes down to a simple and specific commitment to a traditional idea of marriage, and it probably doesn't have the far-reaching implications that people assume.
Of course, his donation could have been motivated by complex ideologies. In that case, if we're going to hold people to such a high standard on the moral checklist, then I would worry more about the things that we don't know than the little glimpses we have into the inner lives of our leaders.
It's interesting to see where all this public discussion is going.