1. Being gay is not natural. Real Americans always reject unnatural things like eyeglasses, polyester, and air conditioning.
2. Gay marriage will encourage people to be gay, in the same way that hanging around tall people will make you tall.
4. Straight marriage has been around a long time and hasn't changed at all; women are still property, blacks still can't marry whites, and divorce is still illegal.
6. Straight marriages are valid because they produce children. Gay couples, infertile couples, and old people shouldn't be allowed to marry because our orphanages aren't full yet, and the world needs more children.
7. Obviously gay parents will raise gay children, since straight parents only raise straight children.
10. Gay marriage will change the foundation of society; we could never adapt to new social norms. Just like we haven't adapted to cars, the service-sector economy, or longer life spans.
More (12 reasons total).