Yes the Bible says gay marriage is wrong.
But, often ignored fact, marriage after someone has been divorced is equally wrong according to the Bible.
If your a Church preaches about divorce and re-marrying being wrong, they are indeed a rarity.
Still I am not going to say doing so should be illegal. However, I will draw a line when it includes minors. That should be regulated! One can deflect with the 2nd Amendment all they want. Law abiding citizens owning guns does not give an old geezer the right to marry a minor!