What would you call them then?
From Reuters:
U.S. Defense Secretary Donald Rumsfeld argued on Tuesday that the guerrillas fighting U.S.-led foreign forces and the American-backed government in Iraq do not deserve to be called an "insurgency."
Asked at a Pentagon news conference why he did not think the word insurgency applied to enemy forces in Iraq, Rumsfeld said he had "an epiphany."
"I've thought about it. And, over the weekend, I thought to myself, you know, that gives them a greater legitimacy than they seem to merit," Rumsfeld said.
Rumsfeld instead referred to the guerrillas in Iraq as "the terrorists" and "the enemies of the government." U.S. military statements also have referred to insurgents as "anti-Iraqi forces."
If calling them insurgents lends them too much legitimacy, I would call them "the enemy". They're shooting at our people. They're trying to destroy infrastructure and kill innocent civilians. If that isn't an "enemy", then I don't know what is.