Cliff, I think you are right in saying that we need terms which (a) accurately describe the enemy we face and (b) convey to the average person that the enemy must be taken seriously. I think the answer stares us in the face. We should call them what they call themselves.
Recall World War II. Just weeks after Pearl Harbor, the 1942 Declaration of United Nations described Fascist Italy, Nazi Germany, and Imperial Japan together as “brutal and savage forces seeking to subjugate the world.” Besides that, we let them have the names they chose for themselves. “Fascist” became a vile word because the fascists themselves made it so.
Same goes for the “Wahabis” and “Hamas” of the Sunni and the “Mullahs” and “Hezbollah” of the Shia. I don’t see the point in reviving the terms of another era. There are important differences between the Wahabis and the fascists, because the Wahabis are in many ways much worse, when you get right down to it. Today’s “savage and brutal forces” are the Janjaweed, and the Hamas, and the Mullahs, and the Taliban. History will preserve all their names in infamy.