Chemical weapons different
Syria’s use of chemical weapons is an act outside of any normal situation. Violence caused by the use of traditional weapons is bad enough, but the damage they can cause is understood, documented and controllable. Whereas the damage and violence caused by the use of chemicals or biological weapons cannot be controlled or limited. Any authority that attacks its foes with chemicals or biological weapons not only puts their enemy at risk, but any people, foes, neutrals or friendly, within the lifespan and impact zone of the agent at risk.
Any authority that will use chemical or biological weapons, especially against its own people, is operating outside of any thought process that can be understood by anyone else. The authority that directs the use of chemical or biological weapons must be stopped and deterred from any further use.