Hi, anti-vaxxer here. It's never really been about "the mercury". Its about having a perfectly normal child that suddenly "regresses" after shots, be it through autism, sudden seizures, new allergies, or even death.
Don't take my word for it, the inserts themselves state most of the risks[0] from death all the way to shedding live bio-engineered virus onto the immunocompromised (so much for that argument). Plus part of the deal that the government had after removing vaccine manufactures for any liability for injury or deaths was to have a "database" of reported injuries for the public to analyze the safety for themselves[1]
So you see, we are not crazy, we are people that have children and we research what we believe is best for them. Following one's conscious is a one of the ideas allowed by our founding fathers. This image sums it up best: https://i.imgur.com/PdsJLLD.png