The problem is also that people will probably paint calling homosexuality a sin as being homophobic, when I couldn't care less about gay marriage (as in they should be free to marry).

I encourage having people be free to do what they want to do. But that also includes religions being free to not want to participate in something they find sinful (so long as it doesn't hurt someone). And by hurt, I mean things like raping, and killing etc, not just offending someone. There is at least one religion that offends me, doesn't mean I want to see them having their rights taken away just for that.