The problem with this type of thinking is simply ignorance. Ignorance as in "you don't know". Case in point, a century ago (and older), children were dying left and right of various diseases. Most of them are now mostly gone because of the early vaccinations that everyone gets. In countries where this doesn't happen, those kids still die.

Now say you grew up in a country like that. Everyone has mandatory vaccinations from young age and are protected from things that used to kill a good chunk of the population. You grow up with this ignorance of an otherwise mass death of children that used to happen all over the world for centuries. You grow up and don't see this death, you're ignorant of it and you're full of these vaccines that you received as a child.

So why wouldn't your ignorant self say vaccines don't do anything. After all, you don't see anyone dying. You spout nonsense like vaccines do shit.

Now let's say people take you seriously and stop vaccinating children. Magically these diseases come back because they don't care that you're ignorant, they only want to infect and spread to everyone else. Mass deaths begin again.

Then another cycle starts where vaccinations are reintroduced and, once again, a new crop of ignorant people comes up.

You're basically the animal on the right. Problem is that if someone takes you seriously then people are going to have to die before you realize your mistake.