Here are the claims that have been made recently by people who oppose gay marriage:

Homosexuality is the same as bestiality.
Homosexuality is a sin that is second only to murder.
Legalizing gay marriage will lead to legalizing polygamy.
Gay politicians want to abolish traditional marriage.
Homosexuality is caused by the same "impuse" that causes crimes like arson.
Homosexuality is three times more dangerous to your health than smoking.
And my personal favorite, a "gay lobby" pressured Pope Benedict into resigning.

Sounds kind of ridiculous when you lump them all together, doesn't it?

My opinion? Anti-gay marriage people know that the days are numbered for their cause, and they're getting desperate.