This being the internet, a lot of the responses were hate (in any and every direction) or bad puns or otherwise useless. But I only want to talk about one common thread since I think it’s a textbook, but unrecognized, case of derailing. (That is, it’s not in the canonical list of derailment strategies in Derailment for Dummies.)
The response I want to talk about is “He has every right to support Proposition 8.”
What does “He has every right…” mean here? It could mean the literal thing: He has a right (moral or political) to have this opinion. But I doubt it. Certainly in this context, nobody was suggesting we pass laws to outlaw the opinion that gay people should not be allowed to marry.
The real point, I think, is in the implied continuation, “He has a right to his opinion and therefore (sic?) you’re somehow wrong to have disagreed.” This is pure derailing. After all, what are you likely to respond? “Obviously, he has a right to his opinion. I just think he’s wrong…” But now — by magic — we’re no longer arguing about Proposition 8 or gay marriage. We’re discussing people and their right to opinions. We got derailed.
The point is this: saying “He/I/Whoever has a right to have an opinion” is not a helpful response to criticism. Criticism is (generally) an attempt to engage. “So-and-so has a right to an opinion” is an attempt to disengage. Better responses include reflection, argument, consideration, discussion, etc.
Because, to bring this back to the present case, opinions matter. They change people’s lives. In the case of Proposition 8 (and other such laws), they affect a vast number of people who cannot enjoy the rights and privileges marriage brings. If the best response you can think of is “He has a right to his opinion,” please try harder. That response doesn’t affect the real conversation — Will we or won’t we give equal rights to the people who currently lack them? — at all. That response is merely hot air.