Too many people who don't want gays to get married will yell something like: "Gays are ebil cuz o sodom n gomorrah thats why god destroyed them cuz they were gay'.
No. The book of Genesis never specifically says for what reason they were destroyed. The reason is not specified until Ezekiel.
"Behold, this was the iniquity of thy sister Sodom, pride, fulness of bread, and abundance of idleness was in her and in her daughters, neither did she strengthen the hand of the poor and needy. And they were haughty, and committed abomination before me: therefore I took them away as I saw good."
In those days, 'abomination' was defined as 'any action that offended God', not 'being gay.' Back then, abomination included eating shellfish, having a disobedient child, and having sex with your wife while she was on her period.
In short, Sodom and Gomorrah were not destroyed for being gay. They were destroyed for being complete assholes.