"Four people who received Pfizer's vaccine developed Bell's palsy, a form of temporary facial paralysis"

The trouble is, this one's a bit different than a slippery slope argument. We'll have to decide whether we want to allow fringe news at all.

If YouTube announced tomorrow that they would ban opposition to the new vaccine, would that feel as comfortable?

Do you think people should be able to make up their own minds? Unfortunately, all of those actions you mention run contrary to that premise.

E.g., look at medical licensing. One could oppose it, on the grounds that people should be able to make up their own minds as to whether somebody is competent to perform surgery on them. Saying that a person can't call themselves a medical doctor is just denying them freedom of speech! Who is the government to come between private parties! Etc, etc.

But in practice that would lead to incredible harm for little gain. I think individual freedom is an important value, but not the only one, and that real-world concerns require balancing values.