I reject the notion that there are no good reasons to prefer the preservation of marriage as currently defined, and that those reasons have anything at all to do with hate.<quoted text>
I don't see the distinction you do, but it shouldn't be a stumbling block either way. I'm good with you saying that the institution will have changed. I welcome that change.
I agree with the first clause. Regarding the second, I agree that people don't need to be feeling hatred when they facilitate Christian homophobia. I don't think that either you or Riverside Redneck is feeling hatred when you do that, although I do think that the original source of those ideas was hate filled.
But what I do criticize you and him for is fighting against other people's happiness for what appears to me to be to no good reason.
It helps to call hate what it is. If the claim has no merit, it will fail to resonate with people, as when Christians say that we hate their god.
But if the claim does have merit, it will spread through the culture and become the dominant meme on the matter, which I believe is what is happening. I think that the Christian church's counterargument - that its message is not hateful, and that it a loving institution - is being increasingly rejected.
Regardless of whether the (hate) claim has merit, it can and is useful for intimidation.
It is used much in the same way that the fear of being called a racist has been used for certain social and legal causes.