Bombing hospitals, clinics, or ambulances is a war crime but for Syrian, Russian, & US-coalition bombers in Syria it is an established military pattern to target them as part of systematically targeting civilians. Assad propagandists justify these crimes against humanity by claiming they never happened or that medical facilities were being used to harbor terrorists. They always have an answer for everything: deny, deny, deny.
What Syria, Russia, & the US-coalition are doing in Syria has precedents with Israeli bombing of medical facilities & ambulances in Gaza, with US bombing of the same in Iraq & Afghanistan, & with Saudi-coalition bombing in Yemen. There really is no way to force militaries to conduct war in a humanitarian way regardless of international law. There is no such fiction as a humanitarian war. The only principled stance is to stand steadfast & oppose all foreign military intervention. That is not a pacifist stance. People have a right to defend themselves by any means necessary. But there isn’t a time in recorded history when bombers were ever used for self-defense.