It's not that simple. Marriage is not a right. For anyone. It's a social construct. You can't engage in the "active suppression of other people's rights" when there is no right involved.
It's a social construct that has been turned into legislation, which then defines the rights. Some people have the right to get married, and some don't.
I see both sides of the issue have valid arguments, but booting somebody out of an organization for having a different political opinion does not speak of a "culture of openness." It's open and inclusive until you vote in a way we don't like. Wow.
When your organisation is built on the concept of "openness and inclusiveness" then it seems strange to me for them to allow someone - their leader - to hold an opinion which is arguably not about those things.
Is the only thing worth being intolerant about, intolerance itself?
Anyway. This is a complicated issue; I still am not sure how I feel about it. I feel sorry for Brendan because of the situation he was put in - but I am probably more sorry for an entire class of people who are denied rights to engage in a social construct of their own free will for some arbitrary reason like the gender of the person they want to be with. I don't know how to do this kind of moral calculus.