John Quiggin nails it

On the Republican anti-vaxers:

The logic of the issue is pretty much identical to that of climate change, gun control, and other policies disliked by the Republican/schmibertarian base. People want to be free to do as they please, even when there’s an obvious risk to others[,] and don’t want to hear experts pointing out those risks. So, they find bogus experts who will tell them what they want to hear, or announce that they are “skeptics” who will make up their own minds.