"They" always tell us there's no such thing as a slippery slope. Accept same-sex marriage, and that's as far as it will go --marriage won't be infinitely malleable as those freaky wingnuts claim. But here --courtesy of course of the Dutch-- is a married "trio." (Less importantly, how did this particular guy get one woman, much less two, she asks rather uncharitably?)
And as long as we're on the topic of slippery slope, here's Paul Greenberg on fetal farming.