"Slippery slope" is so overused that we forget the original analogy. It needs to have a pressure in one direction and very little to resist that pressure. That

"Slippery slope" is so overused that we forget the original analogy. It needs to have a pressure in one direction and very little to resist that pressure. That is, it has to have a slope and that slope has to be slippery. In this particular case, it's a slipper slope on which we already have a ton of momentum.