"There's a difference between seeing someone do something stupid and demoting/anathema'ing them. Then, there's this thing where you know this guy could rise atop you and you specifically demote them. One is good Imperial RP, other is being a douche. It's not against the rules, but like I said, let's call a spade a spade."
Both of these situations are instinces of good imperial roleplay. Whether the player is playing the character with his/her own persona, its still roleplay within the game.
With some of my Imperials I, stole from others, looted others, denied promotion, demoted, anathed all in the benefit of my own character. With one High Priest I paid someone to kill other Sect Leaders. I knew little of this felar ap dreadlord, but from what I hear on the boards, he was still roleplaying a viable character.