Most of the time people's "slippery slope" arguments are based on their own emotional hysteria and not much else. In my mind, a true slippery slope must establish causation between a series of points, based on an original premise. If one's opponent can debunk even one point in the chain, then the whole premise is wrong... and if the slippery slope cannot even be proven with evidence in the first place, then it's opinionation and nothing more.
Slippery slopes are usually due to lack of creative thinking. When I see one, I'm immediately on guard.