Let's make on thing perfectly clear here. There is no such thing as gay marriage.
It is just marriage.
And here in the U.S. it is quite simply a contractual agreement that two consenting adults enter into. That's it. And the rules say that you can't discriminate against someone in a contractual agreement. Done.
The contractual agreement has nothing to do with whether or not you love each other or whether or not you are sexually attracted to each other. It is an agreement that says you and I will share responsibilities for each other. It's actually quite nice in its simplicity. At its basest, "If you throw up, I will hold your hair back. If I throw up, you will hold mine."
Not for nothing, you might think that by saying "I am a straight person who supports gay marriage" you are helping the cause but I really don't think you are. You are perpetuating the myth that there is something different in the relationships that gay people have versus their straight counterparts. Better to say "I'm a human being and I like the idea that people want to take legal responsibility for each other."
And guess what, I think it's great when people who get married actually love each other and are sexually attracted to each other. The lucky ones are.