Here's an article about the ten most controversial Wikipedia pages (judged by the numbers of "reverts," i.e., the number of times things were changed back) according to a study. Mohammed, Jesus and Christianity all made the top ten on the English list. Another religion-related item in the top ten was circumcision. Wow, people argue a lot about religion. Who knew?
I should add that the #1 most controversial page wasn't about religion, but about that other controversial subject, politics-- specifically, the page on George W. Bush.