If you really don't know what the big deal is about gay marriage, please, PLEASE, take the time to educate yourself! The first place to go is this letter, written by some law professors who were expressing concern about gay marriage in New York (the concerns are valid for the entire country).
Then check out what has happened in Massachusetts since they made gay marriage legal. Is this really what you want for our country--for your children? If so, Barack Obama is your guy!
Unfortunately, on this issue, Romney isn't much better. For those of us who oppose gay marriage, our only hope is that Romney will pay some attention to his base.
Finally, if you really need to see the true face of homosexuality--as opposed to the white-washed propaganda you get from the media and Hollywood--you could check out San Francisco's annual Folsom Street Fair. Hint: when gays put on their own festival it is never about loving, monogamous families. This is the side of homosexuality that the media doesn't show you.