Honestly, why someone would be emotionally invested in vaccines one way or another, I have no idea - I honestly suspect that some people are either just trolling or bored if arguing about something as insignificant as "vaccines", especially when they're not a doctor or affiliated with the medical or vaccine manufacturing industries in anyway.
It's part of the current rebellion against self-described elites ordering us around, I think. There are a huge number of books coming out now against so many medical involvements in our lives -- all the screenings, all the false positives, all the vaccine shaming and guilting and legal actions against ordinary citizens. The determination to "treat" healthy people to make more money for the medical industry; the prescription of huge amounts of harmful meds we'd be far better off not taking at all. I've read some eight books on what is being called the "overtreatment" problem, and have some 15 to go. I don't consider this a conspiracy theory in any sense: it's a social problem of overcontrol by an "elite" segment of society that wants to control us all so they can maintain their high income and power. They fight back fiercely against any sign of independent thinking on the part of their victims, the citizenry. I think they are riding for a fall; I hope so.