Sounds like an arbitrary distinction, but in any event, it was the OP who used "slippery slope" to refer to going from "congestion pricing in NYC" to "they're going to take my car."
The distinction is important: a change in a law isn’t always a slippery slope towards other things. Implementing congestion pricing isn’t a slippery slope towards seizing peoples’ cars, which was GP’s point (which I agree with).
To make it obvious: universal suffrage is a change that happened, but it wasn’t a slippery slope towards giving dogs the right to vote. Some changes result in new stases.
The distinction is important: a change in a law isn’t always a slippery slope towards other things. Implementing congestion pricing isn’t a slippery slope towards seizing peoples’ cars, which was GP’s point (which I agree with).
To make it obvious: universal suffrage is a change that happened, but it wasn’t a slippery slope towards giving dogs the right to vote. Some changes result in new stases.