By now everyone has heard the arguments on both sides. The one that I think is the only one that will have a hope of changing any minds is that the US was based on the idea of more freedom for the individual rather than less, and despite nearly eight years of an administration that has done it's best to scream Freedom at the top of it's lungs while simultaneously eroding that freedom at a frightening pace, this core value holds true. Does anyone think that this would be a better country without women's sufferage, the abolition of slavery, civil rights, and habeus corpus? Anyone, that is, who isn't doing a bang-up Archie Bunker impersonation?
Marriage is two people committing to a long term relationship, in theory for the rest of their lives. It brings stability to society and security to child-raising. I'm not sure how a few Biblical passages that also ban the eating of shellfish and keeping your head covered rate with the other big social contract elements of Judeo-Christian culture, the Ten Commandments.
Of course, the horse has left the barn years ago, and just like the list of improving freedoms above there will be those who continue to fear power in the hands of people who aren't exactly like them. These are people like the Neo-Nazis, who would encourage that I be beaten or killed because I have dared to marry and produce offspring with a non-Caucasian woman. Or those who say that marriage is for propagation of children only - in which case I clearly should get a divorce because I've been clipped.
You may come up with all of the arguments against gay marriage you want, but it all comes down to the simple fact that those who fight against it are on the wrong side of history. It's been demonstrated again and again. Are there causes that we should fight against? Of course - any unequal power situation (polygamy, child brides) should be avoided, but gay marriage has no more of a power balance issue than regular marriage.
Gay men and women are exactly the same as heterosexuals in every way other than sex and reproduction. I've had landlords that were gay, played in bands and sung in choirs, gone on trips, drank beer and dined, and I'm here to tell you that they are people just like you. They have preferences just like you. Unlike you (assuming you are straight), they are banned from hospital beds, from inheritance rights, from family health plans.
How the hell does allowing these rights to same-sex couples hurt you?
More importantly, do you really want to be the person who rails against a particular group because they aren't like you? Because that's what the Klan does. Perhaps you'd be better served by getting to really know a few gay people and take a hard look at your own behavior. Hate is ugly, acceptance and tolerance are not.
Besides, you really aren't going to end up having any choice, any more than the people who didn't want blacks or women to vote did. Portland has it's first openly gay mayor entering office in 2009, how long will it be until they get to the presidency? Don't be ignorant, be open.