I think these comments by Diaz are very telling.
And now for my two cents:
Gay marriage supporters look at gay marriage only as a means to make things "fair", to elevate homosexual unions as something that is natural and equal to heterosexual marriage. The idea to recognize the differences between the two is seen as discriminatory. Both are the same to gay marriage supporters and society should reflect it as such, but what really is their opinion about marriage to begin with?
I wouldn't be surprised if it was rather low.