Terrorist is a selectively applied label and ISIL is most definitely not one, let me explain. Donald Trump said "Don't Just Kill ISIS... Kill Their Whole Families" What does that make him?
The generally accepted academic definition of "terrorism" is "acts committed by non-state actors, targeting non-combatants for the express purposes of furthering or promoting a political agenda." It's pointless to classify terrorist groups in the first place. The reason there is no such thing as a terrorist group is because, especially in the case of insurgencies, there is no such thing as a non-terrorist group. Both sides often intentionally target non-combatants as a means of furthering their political goals. Although stronger sides tend to do it less since they can feasibly target actual combatants. The first reason to ditch the "terrorist group" label is because it isn't a binary classification. All belligerents use terror to a greater or lesser degree. Because of this, it becomes deceptively easy to apply the terrorist label if it suits one's particular purposes. Moreover, establishing a false dichotomy renders acts of terror from strong belligerents "unthinkable," which forestalls accountability for things like targeting hospitals.