Eugene Volokh (who's for gay marriage) points out that it's silly to deny certain legislation or decisions as not leading to a "slippery slope," because in fact they do.

I have no problem with this. Hell, I fully embrace it. Gay marriage sends us on a "slippery slope" to all sorts of things. So what. If you want gay marriage, you can't deny the slippery slope. Slippery slopes lead to all sorts of things, good and bad and are a part of society and even progress. Haven't these people ever seen Connections?