If you're comparing Chaos to Terrorism, then would you also prefer that we called Terrorists by a different name too? Chaos are traitors, doesn't matter if calling them that hurts their ego. If they didn't want to be called traitors because it hurts their pride... maybe they shouldn't have done so much betraying.
That's not the point, in a real world comparison we'd be saying terrorists don't call themselves terrorists. It doesn't mean they aren't or we don't call them that. How is this so hard to understand?
Don't get me wrong. Chaos is free to not call themselves traitors, but the game and the rest of the community will call them what they really are.
I agree, but I think the Emperor did influence Lorgars decisions. He castrated him in front of his men and you, as a leader, never do that. Talk about infantilizing someone. Your dad comes to your work, bitch-slaps you infront of everyone, and tells you that you can't play in the sandbox anymore. I understand the frustration and sadness he must have felt, but it does not excuse his actions. The ultimate irony is that the fruits of his labor, the imperial creed, are used to this day. Nevertheless, I think such believes were inevitable for mankind.
But then ork boys should be called something like "stupid brutes", Dire Avengers should be called "pantsy (or something more homophobic) space-elves", and tacticals should be called... "smurfs" (yeah yeah thats Ultras but whatever)? It makes no sense whatsoever for basic CSM to be called what the Imperium would call them to slander them. It looks dumb. Also regarding the lore, the Word Bearers were one of the most humanitarian Legion, and Lorgar obviously thought the Emperor approved of his way of doing things (not facing any serious censure or anything for 200 years!). From their perspective, out of nowhere the Emperor and the Ultras came and killed perhaps millions of 'his' people. If that is not a stab in the back I don't know what is? And they only told him about what they had done after they did it. No warning or anything. The WB were clearly betrayed, and of course the loyalists don't see it that way. That's the point. Tacticals are as much 'traitors' as their equivalent CSM brothers.
The entire point we are making is that the game allows us to play from Chaos' PoV ie, not the Imperium's. Though Imperium novels frequently refer to them as traitors, Chaos novels do not, for example in the book actually named Betrayer they don't ever actually refer to themselves as traitors. We don't care if you call Chaos Marines Traitors or if anyone else does, the point is from the perspective of our own lore we wouldn't. We're here to play our own faction, not as the backdrop of a Space Marine power fantasy.
So regardless of lore disagreements, which are essentially opinions, let's consider a few measurable facts. First is the most subjective, the biggest defenders of Traitor as a class name appear from their avatars and statements to be IoM fans primarily. Meanwhile the actual faction's fanbase, and more reasonable Imperial fans, seem to mostly be against it. The name change was meant as fan service for Chaos, but it looks like only uncompromising Imperial fans actually like it. Secondly we actually do have numbers, Djemo-SRB ran an open poll that asked a simple question, "Do you like the class name Traitor?" Less than 30% of people said yes. I ran a poll that asked if people would rather the class be called Chaos Space Marines, about 90% of people said yes. This shows a clear and measurable deficiency of approval for a name change that was primarily suggested and defended by loyalist fans, but is distinctly unpopular with the actual player segment it was meant to please. Third, it was never a popular submission in the first place, there was overwhelming support for Legionnaire, Legionary and Marauder. Traitor was part of a braket of names that got very little support, and once again this appears to have been almost entirely from IoM fans. So it never was popular, isn't and unlikely ever will be, why should a faction be made to keep a class name they don't like, that doesn't properly represent their own faction's lore, and only seems to be liked by people that dislike the faction itself?