Oh for fucks sake.
This is gonna piss someone off, but look, these people are fucking desert savages. You can politely pull them aside and ask them to please stop using chemical weapons on civilians (and we have) but that's not something they process or respect.
Leaders like this respond to shows of force and nothing else.
Now, on the other hand, "knock this shit off or I burn your fucking world. Here's a shitton of tomahawk missiles to illustrate my point" is a message Assad can understand. You have to speak his language.