Darwinism has a proper place in this discussion, like George says. For instance, if somebody with a measurable IQ of under 70 commits a crime, they are treated differently than ordinary folks.
                  It's the same was with people who are addicted to some looney religious conviction. Because we equate religious rights with civil rights, we tend to give those people a pass.

                  At the end of the day, if there were very many of them, ordinary criminals would be locked up, with criminals with low IQ's and looney religious convictions would be free to go forth and procreate. At some point in time, most people would have low IQ's and looney religious convictions.