I tend to argue that “slippery slope” is not actually a logical fallacy the way others (e.g. straw man) are.

A slippery slope is often a legitimate concern.

Using it as the sole means to shut down an idea is often disingenuous, but so, too, is shutting down any concerns of a ”snowball effect” by calling it a logical fallacy.

Like any logical fallacy, the slippery slope is about the general validity of a logical inference - and not about the truth of its conclusion.

The slippery slope fallacy argues that "if X happens, then eventually Y will happen as well", where Y is a more extreme version of X. This is not a valid logical inference.

That doesn't mean that there are never cases where X actually leads to Y. Just as calling out "appeal to authority" doesn't mean that an expert isn't often right, or just as "correlation is not causation" doesn't imply that correlation is never causation.

The recognition of the phrase as a logical fallacy comes after the phrase starts to be widely used, not the other way around. If everyone starts saying "snowball out of control", then eventually the fallacy will be known as "snowball out of control" fallacy instead.