I thought the same, but I think it's a pretext. They are not angry at Cassian for using that name but at everyone who sully their teacher's name saying he deserved his death. Turning their anger at Villain Cassian is just a subconscient way to feel less powerless I guess.
Im not sure, but villain names to villains are important, Villain names are part of their powers ig, when cassian called himself something( a simple name) not something like shadow lord, the name Cassian indicates a special meaning, the story said of a myth(?) Or rumor that a villain names himself after a dead(?) psyker will give him additional power, basically mc purposely and publicly named himself Cassian as in Cassian the corrupt Psyker
Cassian was his REAL name as a hero, not just a name he made to be a hero. Now they're telling Villian Cassian he has to Change his name?
Imagine his name was like John or something and try went up to him and said "You need to chantre your name because we knew a famous John who was very good and you're a horrible person and don't deserve that name"
It's really a ridiculous concept when you Thi k about it. Do they expect me to believe that the Hero Cassi an is the ONLY one in the world named Cassian? I betcha mothers named their kids after the hero that saved them and stuff.
What I'm saying is I woulda fought them for the sheer audacity.