Unless you are standing at the top of a steep hill during a rainstorm, you don’t need to worry too much about slippery slopes.
Don’t get me wrong. It’s a great image. You put one foot forward — say, by forcing health insurance companies to cover birth control — and WHOOSH, you slip. Before you know it, you’re at the bottom of the slope, where women murder toddlers for fun. Or what’s the one about gay marriage? If you let gay people marry each other, you also have to let people marry turtles? Someone actually said this.
Political positions — even apparently harmless ones — can have serious consequences. Occasionally the doomsayers are right and the slope between here and the collapse of civilization is indeed slippery. But usually it’s more that you’re stuck listening to some asshole who can’t argue properly and therefore hopes you won’t have too many follow-up questions when he gets to the part about how sales tax leads to gum disease or atheism leads to nihilism. It’s a really common rhetorical trick. Don’t fall for it.