I've observed this for a long time. The homosexual movement can basically be summed up this way: "Accept me on my terms."
Same-sex marriage isn't about partner benefits (except possibly AIDS, I know in the 80s, when gays still didn't want anything to do with marriage, there was much talk about partner benefits). It's about society (I guess in the modern age, that means government.) putting its stamp of approval on your relationship. I'm sure it is to make up for some lack of approval somewhere else (Daddy, in many cases) but it's really indicative of some serious psychological issues.
I think it's a case of trying to "norm" the outside world to conform to what they are thinking and feeling inside. But what interesting to me is that no matter what society does to accommodate gays and lesbians about accepting them, it will never be enough. Why? Simply because as long as the laws of nature work as they do in reproduction gays and lesbians will feel a disconnect.