"Terrorism" isn't the issue here. Extremist Islam is.
Terrorism is what weaker groups resort to when they have no other means. Whatever you think of their issues think of the Basques, think of the IRA, think of the Symbionese Liberation Army.
War is what stronger groups resort to -- whether American revolutionaries, Nazis, whatever.
There's an intermediate category, for example the French Rèsistance, but their focus was not on the populace but the invaders. (I am not quite sure where the Celtic Breton population in France is in regards to French rule.)
I would disagree with you on this point. Terrorism IS the issue, in my opinion, and Islamofascism is the proponent du jour.
There are plenty of examples of armies taking the lives of civilians who are not directly “involved” in combat, but the specter of mass murder of a completely uninvolved civilian population is much clearer today than at any point in history.
I see the point you make, but I think it is much more serious in the direction of terrorism and not Islam.