Um, folks... lafemmefatale's actual
question, which this hot-button issue appears to have prevented anybody from actually reading, is this: how does somebody who's pro-gay marriage approach a debate where they're assigned to argue the anti-gay marriage side? She's not asking your opinion. That's been done before.
First of all, I'm PRO same-sex marriage. They're people with whole, functioning sets of emotions, just like straight people, and they should be free to express their love for each other just the same way I can. For me it's not about legal protection, it's about self-expression. That's my OPINION on the matter.
Now, how I'd argue this if I had to argue against gay marriage is this: cultures are based on traditional families. With some small number or exceptions, children are raised in the context of one mother and one father (even in the case of divorced families, that context still exists). To replace that with a potential context of two fathers or two mothers is to undercut the whole structure of society. We just don't know what result that would have if it took place in a significant percentage of families, but the incremental increase in individual freedom is not worth the extreme risk to our culture and society.
I'm glad I don't have to make that argument, though, because it kind of makes my skin crawl.