"Rebel-held Syrian towns." 

Here the lie is even more extreme than it was in the case of east Aleppo. At least in that instance there really were a significant number of rebel factions fighting along side the terrorist groups. It's completely different now. 

The territory to the west of Aleppo and extending into Idlib province is almost completely under the control of the radical group called Islamic Front. Think of them as a more politically-savvy version of Islamic State. The goals of the two are the same, but Islamic Front has been smart enough not to mount terrorist attacks in the west. Hence they're not officially on any country's terrorist list. Nevertheless they are accused of atrocities and war crimes, including the use of poison gas. Islamic Front's goal is to destroy the secular government of Syria and establish an Islamic caliphate under sharia law over all of Syria.

Peace will not return to Syria until Islamic Front and Islamic State are both defeated, or they surrender.