You gotta keep in mind that the ratio of 'stupid', or mentally ill, or etc. people ain't different in religious people than anywhere else ...
Except these are not instances where there are a few crazies in otherwise perfectly normal congregations. These people belong to denominations that
specifically teach that God will heal instead of doctors.
You cannot honestly claim that, when a Jehovah's Witness child dies because his parents refused to let him receive a blood transfusion that this is the result of a single case of crazy within statistical norms. The institution actively promotes the neglect, and even threatens its members (with the threat of Hell, or in the JWs case, shunning by the family's entire social network).