approval of which would suggest approval of deviancy and thus marginalize those of non-deviant lifestyles.
Ignoring the fact that you can't actually marginalize non-deviants, your statement is incredibly hypocritical. According to you, it's okay to take away people's rights (thus marginalizing them) to do what they want with their lives, because this somehow marginalizes people who are not affected by it at all. If we allow "deviants" the freedom to do what they want with their private lives then "normal" people are somehow marginalized, but if we ACTUALLY marginalize the deviants then it's okay because we're on a moral crusade?
The solution is to just say fuck it and let people do what they want with their private lives. Do I particularly approve of someone who wants to sit in their basement and masturbate to animal porn all day? No. Does this affect me in any way? Do their actions have any influence on my life? NO! It is their life and their choice to do what they want. Who am I to say what is right and wrong for them to do with their lives?
In the words of Frank Reynolds from It's Always Sunny in Philadelphia, "Who gives a shit if gays want to be miserable like everybody else and get married? Let 'em do it! It's no skin off my ass!"