> So the same action is called by different names depending on who does it?

Exactly. "Terrorism" is just a label to describe the parties involved, not a value judgement. A death is a death whether it's from guerilla warfare, a mass shooting, terrorism, an accident, or a full scale war.

Well, if "terrorism" is just a label, then it shouldn't matter if war is labeled terrorism on a larger scale.

I don't see what you gain by doing so other than producing more emotion which isn't particularly helpful. We already have way too much emotion surrounding this word. A nebulous definition makes the problem of terrorism harder to bound and develop strategies to deal with.