Let's take the slippery slope the other way.

 

If the legalization of gay marriage has encouraged people to be gay, this encouragement comes from allowing people to have sex before marriage.  Therefore if we outlaw gay marriage, we should also outlaw people having sex before marriage.  Of course, it can also be said that having sex for reasons other the procreation is deviant in itself.  Therefore people not trying to conceive should also not be allowed to have sex.  So by banning gay marriage, we're going to slowly and surely bring legislature into the bedroom.  And don't tell me politicians wont' be pushing for it.  Rick Santorum is a name that comes to mind quickly. 

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