The more I study human history, the more I am convinced that the slippery slope is not a logical fallacy.
There are principles and once those get principles get trampled in the name of expediency, it becomes easier for the next person the trample them further.
Like when the American right-wing came up with the "domino theory" to justify paying any cost to defeat communists in Vietnam, since to failing to stop them would inevitably result in communists ruling the entire world.
And then the US lost the war, went home in disgrace, and the promised cascade of falling dominoes never happened.
Part of the reason why the dominos did not fall was that it extracted a very high cost. Vietnam was devastated by the war. Same thing with Cuba. Although not a direct invasion, the US sanctions on Cuba extracted a high cost.
Sometimes resistance can make a slope less slippery. With Donald Trump’s election in 2016, I believe the US was on a slippery slope to a very bad place. A lot of stuff were being normalized that should not be (overt racism). However, there was a lot of opposition and resistance which has probably helped stabilize the situation.
So no, just because a lot of resistance keeps you from sliding down the slippery slope, it does not mean the slippery slope is not real.
There are principles and once those get principles get trampled in the name of expediency, it becomes easier for the next person the trample them further.