There's a slippery slope version of your argument where your ISP is responsible for censoring content that your government does not like.

I mean, I thought that was basically already the law in the UK.

I can see practical differences between X/twitter doing moderation and the full ISP censorship, but I cannot see any differences in principle...

We don't consider warehouses & stores to be a "slippery slope" away from toll roads, so no I really don't see any good faith slippery slope argument that connects enforcing the law against X to be the same as government censorship of ISPs.

I mean even just calling it censorship is already trying to shove a particular bias into the picture. Is it government censorship that you aren't allowed to shout "fire!" in a crowded theater? Yes. Is that also a useful feature of a functional society? Also yes. Was that a "slippery slope"? Nope. Turns out people can handle that nuance just fine.