I never liked that mechanic. It's been abused in the past.
Seems to me that in the game, we unilaterally tell people "You don't have the right to play in a specific realm/island/guild." Except when it comes to being a priest. They have the unbreakable right to play in their religion, and on their island. They can't be kicked out of a religion by any means short of execution, nor can they be deported from their island. You simply cannot get a priest out of your religion, regardless of what they do. (Unless they slip up and break some rules, resulting in Titans/Magistrates) case against them.)