That makes an assumption that only dissenters are kicked.
He's said he wont just dismantle the religion. Even if he tried the religion could endure as long as the priests were still there. According to the wiki if he fails to appoint any elders for so long that the temples start to decay the game will automatically select a new leader who can then lead the religion.
RE: keeping their traps shut and plotting the downfall:
How, exactly? Am I missing a mechanic in place that allows for the removal of an Elder and countering a hostile takeover of a church?
Infiltrators, rebellions, bribe a judge, bribe a ruler, refuse to invite her to any dinner parties.
