It may be a fallacy to assert that it will happen, but it's entirely logical to observe that the current developments make that eventuality more likely.

Slippery slope goes both ways.

What if giving platforms to Sandy Hook Truthers enable them to recruit more and more crazy people, who would do more crazy things than just making videos, for example, actually seeking out victims of Sandy Hook and harassing them?

...Oh wait.

While not a "ban" they already have taken measures against videos/channels that are primarily gun focused.

Slippery slopes are possible, it’s only a fallacy because a slippery slope isn’t a logical proof. Just like an appeal to authority isn’t a proof but can still lend support to an idea.

Is it a fallacy? China has various justifications for their great firewall. Given all the things the US government has done over the years, I can't say I trust them much more...