Thanks all. Not the answer I was hoping for And yes, I agree with op's rock solid arguments, of course it should be changed. Traitor maybe works in TT, but shouting traitors to your teammates etc... Just doesn't work in an interactive setting. And this is coming from someone who has for some reason always really disliked chaos in all GW games. Anything else than chaos sounds retarded.
Well the actual terminology is Chaos Space Marines in TT. But this is now just a thread in waiting until a new development happens.
With launch around the corner it's more relevant now than it was earlier, this is when people unfamiliar with the lore are more likely to join, I still hope we'll get a set of class names that are actually good/decent to attract more teammates. That and of course for the immersive quality of presenting a faction based on its own veiws of itself, rather than that of its hated enemy.