Stopping my vassals bitching about Crown Authority?

My current character, Kivine, has totally crushed THREE rebelions now. Three goddamnit. And my vassals are still forming factions trying to get me to lower crown authority. WHY OH WHY DO THEY NOT STOP?!

I guess executing every vassal who was involved in the rebelions didn't help... Any advice on making them stop for my son when he comes to power?