A question
By This is not a rhetorical question, nor is it intended to be snarky or otherwise disingenuous.
Why is killing a lot of people with chemical weapons considered so much worse, in terms of international law and geopolitical rhetoric (if not action, c.f. Kevin Drum’s excellent points here), than blowing the same number of people up with high explosive munitions, or machine-gunning them, or hacking them to death with machetes?