I joined this sub because I thought it was funny. I honestly feel weird about it now because of how anti-vax focused it is. I realize now that it isn't as much of a fringe belief as I thought. On the bright side (FWIW), I do think that it has shed light on the type of person that believes in this horse shit though. The perfect storm of personality traits seems to be:

1) Extroverted - there seems to be a desire to "spread the word", which seems to attract those who are more socially inclined. Doesn't mean more introverted people are exempt, obviously. I just think being extroverted is fuel to the fire. You also get to be part of an exclusive club. Exclusive because it's stupid and therefore not mainstream, but people tend to love being part of what they perceive to be a pioneer's path regardless of circumstance.

2) Arrogant - an inflated sense of self-importance and the general belief that they are always correct is what shelters them from new information. Combined with the tendency to be extroverted means there is a greater chance of a community to reinforce the delusion.

3) Being a parent (obviously) - Not really a personality trait, more of a matter-of-fact. Also should go without saying that having children is not a precursor here, but the important thing to note seems to be that that people tend to get defensive over their parenting choices when challenged. Although (again) not inherently a bad thing, not everybody is emotionally prepared to believe they have made a mistake raising their kids.

This is all pretty common sense, guess I just needed to vent.