Why the killers CAN'T kill each other?

Ok so, i'll be answering another big question

But first i have to explain you something, the killers universe is divide in 3 worlds:
-The Artificial World: The internet
-The Mental World: Where the alter egos live
-The Real World: Our reality (Where you and me exist

BOT, Anti, Dark and Virus live in Mental world because they are alter egos of habitants of The Real World (Felix, Sean, Mark and Cry)
But they also had another alter egos:

Felix: PewdieBOT, BeastMaster64
Sean: Antijacksepticeye, Magic Jack, Dr. Schneeplestein, BingSepticeye
Mark: Darkiplier, Wilford Warfstache , Googleplier
Cry: VirusCry, Mad Cry  

The reason of why they can't kill each other it's because they don't belong to the same person, for example, Bingsepticeye is dead , because Anti kill him and they belong to Sean.
Another example, Googleplier knows that he can't kill BOT, because he belongs to Felix, so he will need the help of BM 64 to end him.

But this doesn't mean they can't hurt themself a big example is the dead eye of Anti and the shot that BOT gave to Dark.

Another Fact: The Killers can teletransport to another worlds, when Anti kidnapped BOT, he went to the artificial world (Because of the real page of PewdieBOT) and he also went to the real world searching for something until he found Virus killing her parents.
But also they can posses the person who they belong if they want to, but they don't do it that often because is more easier to them teletransport to the real world than posses the person because they will fight to avoid that.

If you have another question you can ask it, and i'll answer you! :3

I hope you like this explanation