It is a logical fallacy in that the consequences do not logically follow from the proposition. However that doesn’t say anything about whether they are likely to follow in practice, only that there is no logical proof that they follow.
In this case, the arguments against this mechanism are generatly slippery slope arguments - logic doesn’t guarantee the bad outcomes. However it’s quite reasonable to be concerned that the bad outcomes will happen because of the actors involved.
>isn't even really a logical fallacy. In fact, I can think of a number of circumstances where it turned out to be true.
This represents a very common misunderstanding of fallacies, IIRC it's called the Fallacy Fallacy: fallacies don't give you any information about the truth of the conclusion, they only indicate that the logic that ties that conclusion to the premises is unsound. So "slippery slope fallacy" means "worse things don't logical follow in increments from better things" but that doesn't mean that in any real situation "worse things follow in increments from better things" is not true.
The most common example of this misunderstanding is probably Occam's Razor, it says nothing about whether things are or aren't more complex in any real situation, only that it's easy to reason about things if you don't add additional aspects that aren't needed.
edit: here's an example of the slippery slope "fallacy" in action
"First they came for the socialists, and I did not speak out— Because I was not a socialist."