Because Man is a Gregarious Animal
The obfuscation makes this situation complex. It's not at all complex when accurate terms are used. For some reason, the current administration has an aversion to accuracy.
An enemy combatant is a soldier. Someone fighting against their country is a traitor. A citizen has certain rights and privileges. There are procedures for this. First, there's a trial. Then, you hang him.
Seems pretty straightforward to me. You obfuscate when you have something to hide, or when you don't have the ground to stand on.