For most issues in politics, I can understand the other side. I am pro-choice, but I wish we lived in a world where abortions didn't have to happen, and I can understand people not being able to understand that they can't legislate that world into being. I'm pro-gun, but I can see how they scare people, especially people who have enough faith in government to honestly believe criminals could be barred from having guns too. I'm mostly anti-tax, but have doubts as to whether there really is enough philanthropy out there to take care of those who can't care for themselves...
However, homosexual marriage is an exception. For those who haven't heard, Proposition 8 on the California ballot this election would eliminate the right of homosexual people to marry. This is an issue completely removed from those against it (I hope! I haven't seen any reports of homosexual people being pro-8), but there are also no negative externalities. Oh no, more children will be raised by two parents. It's not like the homosexual people would otherwise go find nice heterosexual partners. It's not like anyone is going to take away tax-exempt status from a church that doesn't sanction homosexual marriages, unlike the Yes on 8 smear campaign claims (http://www.noonprop8.com/about/fact-vs-fiction). Gay marriage is legal in California this very day. There are no meteors hailing from the sky, no forcibly taught tolerance in schools, and LA isn't really burning any more than normal. If you're straight and don't have homosexual friends, you probably can't even tell something is allowed that didn't used to be. If you're not, I think it's safe to say that all of the changes you've seen are for the better.
A personal story: two months ago, I went to the wedding of a woman I grew up with in our local Indian community. M- married K-, a Japanese woman. Indians in general are a racist, sexist, intolerant lot, but M- didn't care that so few Indians showed up. She and her family ignored the pomp and circumstance that usually surrounds Indian couples... couples who've frequently only known each other for a few days and are only getting married because they have to. It was the most heartfelt and emotionally compelling Indian wedding I've ever been to, including my own. There is love that is docile and dormant, and there is love that had to fight, and these two clearly had had to fight for everything they had. I've never seen M- so happy, or her father so proud. Part of me feels that marriage should only be for people like that, regardless of gender.
Finally, a good friend of mine (who is straight) wrote this essay on what the right of marriage meant to him and his family. I'm a mean hard-hearted person, and it made me cry to think that this could actually be taken away from people: http://snailprincess.livejournal.com/210625.html
If you live in California, Vote No on 8 and please please tell everyone you know to do the same.