They just become more resolute in their arguments when you present them with contrary evidence or logic. I don't understand the mentality, but it affects my life since I have very close family who are among this group of conspiracy propagators. Not only do they want to fight legitimate medical authorities, but they want to spread their distorted views to everyone who will listen (as this poster is doing). They will spend hours preaching, researching, and defending their philosophy with religious fervor that could be better spent studying how to improve family life, serving others or simply enjoying life.