The simple fact of the matter is that people who deny vaccines are denying others their right to a safer existence, in EXACTLY the same way a drunk driver does.
The hogwash about, "the vulnerable being vaccinated so what's the problem" simply shows a complete ignorance of the issue - in particular the fact that vaccines have very very low efficacy in many CEV, largely because they rely on a well functioning immune system.
As for why anti-vaxxers spread videos like this. It's quite simple - attention. It's how all conspiracy theories develop. Someone wants attention, so they make some shit up. They get others to believe it, which makes them feel powerful. After a while, enough believe this level of shit, so someone makes up something more ridiculous etc etc
The main problem is that often on SM, there are few people arguing against them. Most people would rather ignore and avoid confrontation, so the poison continues to spread.
Personally, I can understand some people, for various reasons not getting vaccinated. The fear is quite understandable.
What I can never condone is those who with zero scientific or medical knowledge, actively campaign against the testimony of the world's experts. Again, part of the reason WHY they do it, is attention, but they are very, very dangerous people and I think this point is often lost.
A neighbour of my mothers lost her life because of someone who persuaded her NOT to get a diagnosis for a medical problem. So instead she took pointless supplements. 6 months later, deteriorating, she got properly diagnosed - it was cancer - treatable if caught in time, but it was too late.