He's doing it wrong. Don't ASK them if they want to convert. Just tell them if they ARE going to convert. And, if they don't, you are going to kill them, their family, and their friends. THAT'S the proper muzzl'em way!
I don't call them "muzzl'ems" without cause. They want to muzzle everyone who disagrees with them. Kind of like demorats.
Just tell them they ARE going to convert.