Hitler taking power and the Nazis invading Poland was also a fallacy. Until it wasn't. The NSA spying on everyone was also a fallacy. Until it wasn't. Go back in time and find other examples.

Any extreme powers you give the government to "keep you safe", they will eventually be abused, first against foreigners and dissidents, then against you.

History doesn't necessarily repat itself, but it rhymes.

Technically, "slippery slope" isn't a fallacy. It's just a name for the idea that one thing leads inevitably to another. It's not fallacious to extrapolate from past experience, even if that extrapolation turns out to be wrong.

I wrote "slippery slope fallacy", not just "slippery slope", for a reason.

Arguing A->B is only a fallacy if no argument for the sequence is provided. A plausible argument was provided here based on prior experience of other governments. There's no fallacy if you just disagree on the probability.

No argument (not plausible, not probable, none) for the sequence was provided.

Communist revolution always precedes communist control of speech.