I oppose gay marriage, but I have no more of a right to force my views on gays than they do on me. The Mayor of Boston does not have the right (legally, as well as theoretically) to ban Chic-fil-A, and I don't have a right to ban gay marriage.
Except you are opposing an otherwise rational state policy (sorry, but there's just no good argument there) based on your own personal religious views -- presumably because you think it's immoral to contribute state approval of a practice you personally consider immoral. You do realize that's not particularly far off from what you're calling "evil"? I realize that, in one case, it's the state refusing to allow a private business based on personal ideology; in another case, it's the state refusing to engage in an otherwise rational social policy because of personal ideology. That's a distinction. It's enough of one that one is "evil" to you and the other is a political view you actively hold?
I hope I'm being clear.