Some slippery slopes are valid; some are not. For a slippery slope to work, the consequences have to be very likely. In fallacious slippery slopes, on the other hand, the consequences are merely scary.
Here’s Ken Cuccinelli with a fallacious slippery slope:
Once the natural limits that inhere in the relationship between a man and a woman can no longer sustain the definition of marriage, the conclusion that follows is that any grouping of adults would have an equal claim to marriage. See, e.g. , Jonathan Turley, One Big, Happy Polygamous Family , NY Times, July 21, 2011, at A27 (“[Polygamists] want to be allowed to create a loving family according to the values of their faith.”).”
Polygamy, or what some call “Traditional Marriage” has already existed as a non-consequence of gay marriage. This means that polygamy is not a stage along the gay permissiveness continuum.
More importantly, polygamy, whatever it might mean, is significantly different from dual marriage (is that a term?). The legal relationships are undefined and it does not exist. Marriage between non-child-producing couples already exists, and differs in no respect from gay marriage–except, perhaps, that gay marriages can result in natural children.
So let’s drop the polygamy business. Yes, maybe it is scary and weird to you. But remember, polygamy is what the Bible sometimes advocates (along with concubines!) and, more significantly, it’s got little to do with the rights of two unrelated people.
Let’s try to be more rigorous and more imaginative. Perhaps Ken Cuccinelli ought to remember that when he opens his mouth to argue, he sets an example for the kids out there. This is a terrible example.