You say that "Allowing it would have harmed no one." Tell me, who is it harming for Brendan to be CEO of Mozilla? The answer is not "LGBT people", because he's already stated that his personal views won't change policy; and it's just not plausible that Mozilla will suddenly start discriminating against people due the the personal views of the CEO.
So we can say, "Allowing Brendan to be CEO would have harmed no one. Not him, not them, not anyone. There are no negative downsides, other than a subset of pro-LGBT-rights individuals who wish to impose their beliefs onto all of society, and onto Brendan in particular, feeling less in control of their lives." How then is protesting Brendan's donation any different than the donation itself?
You might agree with Brendan's views, disagree with them, whatever. But it seems mighty bigoted to start protesting someone else's beliefs; isn't that the whole message here?
EDIT: To be clear, if Brendan ever starts imposing discriminatory policies or the like, I'll grab my pitchfork and join you. Until then, anyone with a pitchfork in hand is protesting not Brendan's actions, but his mere /beliefs/, and that is wrong, and betrays a shocking cognitive dissonance coming from someone who supposedly supports equality and tolerance.
