Extremely extreme extremeism

I've always assumed that the reason people are generally squeamish towards others who take extreme stances on things is because it forces them to confront their own incongruence of behavior with belief. For example, there are parents that do not let their children have any involvement in the celebration of Halloween, citing the explicit paganistic evils portrayed. It occurs to me, however, that there is possibly another dimension to be considered. During our lifetime, we are faced with a number of challenges. Our overall lifetime success or failure is based on our ability to overcome or avoid the complete diversity of challenges that may come our way. Completely avoiding experiences or focusing too narrowly on certain facets of life may actually cause us to be less prepared for future challenges. Could that squeamishness possibly be an internal reaction to the perceived weakness of "narrowness"?