The slippery slope is NOT a fallacy, it is an argument. There is such a thing as a slippery slope. It can ONLY be falsified in the future and only if the thing in the argument NEVER happens. For example, Republicans stone wall gay marriage on the grounds that it is a gateway to other kind of deviant sexual behavior, such as a man wanting to marry an animal. In order for the argument to be invalid time would have had to run out and nobody ever wanted to get married to an animal. But the argument has already been proven correct although the correlation between homosexuals and other types of behavior has not been demonstrated. Observe:
The same people that think the slippery slope is a fallacy operate on a dynamic tautology of the slippery slope argument. If you believe that the argument is a fallacy you should not be acting on it. I am talking about Dawkinites and Hitchenites who never concede when arguing with a person who is not an atheist.