You're getting downvoted because you're dangerously wrong. Yes some anti-vaxers send threats, but the idea that they have managed to silence the mainstream scientific opinion on vaccines is ludicrous. That information is widely available to everybody. I bet you can't find a single anti-vaxer who isn't aware of what the mainstream position on vaccine safety is. Being opposed to the orthodox position is a big part of the appeal!

Also anti-vax isn't something new. It dates back to at least the mid 90s and the original Wakefield paper. There were no cult like organisations pushing it at that time. What did exist was a mainstream media willing to push the story for many years, even long after they knew the original paper was faulty. The problem wasn't born out of fervent zealots, it was created by con artists and co-conspirators in the media who exploited liberal ideas of "free speech" and "media balance" to knowingly spread a conspiracy for their own financial gain. There was no "subculture" at the time. I'm not sure you can even really say there is one now, given that anti-vax is one of the conspiracy theories that has wide appeal across different groups (i.e. it exists across the left/liberal/conservative/right political spectrum).

You are trying to push your own ideological position (more "free speech" is good and will solve the problem) onto an issue, and it doesn't fit what actually happened at all, or what we know about how conspiracy theories spread (it's not a lack of counter-information, because conspiracy theories by definition include the fact that they are being suppressed by central authority).