The thing I've noticed about slippery slopes is the goal posts are also on the slope.

That's not a very impressive article, and it seems like it's a practice that greatly predates modern communication infrastructure.

TLDR: Your rights are routinely violated in a "slippery slope" manner, but the methods and incidents cannot be rectified by the courts because it's hiding under a veneer of parallel construction. It's not like law enforcement is going to come out and say "We're violating your rights." Snowden revelations are a prominent example; Clearview's facial recognition database is another: "Clearview AI used nearly 1m times by US police"

https://www.bbc.com/news/technology-65057011