My family is Mormon. I grew up Mormon. A huge portion of the people I love are Mormon. I am horrified that the Mormon Church has decided to spend so much time, energy, and members' money on trying to pass California's Proposition 8, which would invalidate marriages between same sex couples. Why Mormons have decided to make this such an issue I find deeply confusing, because Evangelicals, who agree with the Mormon position that Gays are bad bad bad, still won't like them, while the Mormon brand has now become associated with homophobia and bigotry. Who are Mormon missionaries going to teach?
At the same time, as this article , this article, this article, and this website show, just because someone is Mormon does not mean they hold the same position as the Church at large. Knowing that someone is Mormon does not also impart the knowledge that they have difficulty with gay people.
The Mormon church has a website, which gives reasons that they feel that people should be against allowing same-sex couples to be wed. Unfortunately, it turns out that most of these reasons are, to put it harshly, lies. Below is a paper, signed by rather a large number of law professors, showing why.
We do not believe it just to mingle religious influence with civil government...
-Doctrine & Covenants, 134:4