gay != pedophile. I think a more reasonable explanation is that people who are sexually attracted to kids maybe seek out positions where they will have authority over them.

Edit: looks like you edited your comment while I was typing my reply. I think the concentration can be explained by the larger amount of boys-only schools, etc., and priesthoods allowing only males. So naturally there is a filter - men who are attracted to young boys will go into the priesthood more than men who are attracted to young girls.