There is no rational argument FOR gay marriage.
Gays CANNOT naturally produce offspring. If they want to have a contract of commitment they can use Civil Unions.
Civil Unions can be crafted to provide every right and privilege that normal married couples enjoy without desecrating the sacred or popular definition of the word "marriage."
Anyone who rejects this politically and legally equal alternative, openly admits that they aren't interested in equality, but rather are seeking to rub the world's noses in their hideous sexual deviance.
Kind of like the kid who was once bullied resorting to bullying others to get pay back.
Irrational, immoral, evil.
It's just that simple.