Good point, but still: does anyone know of any slippery slope [ETA: by which I mean a cascade of self-reinforcing changes in laws or social norms] that most everyone can agree was clearly not-bad? I ask because there are various theoretical reasons why one should almost never expect slippery slopes to have good consequences, but if empirically that's not the case then I need to revise my sociological and historiographical models.

(ETA2: My bad, I confused levels of abstraction; I agree with the criticisms that such an analysis is unfeasible even if possible.)