Parents should always be involved in their children's medical care.
Placing all doctors on pedestals and stating that a parent who disagrees or wishes to try alternate therapies is deluded is no different than stating that the wts is always right and disagreeing with them makes one an apostate.
This dad is obviously well-read and has researched the science. Just because a doctor prefers a different course of action does not make the parents wrong.
Stop being so judgmental. It's not your child and unless you know this man personally you have no business trying to decide what's influencing him or what type of person he is.