Using sarin gas to show rebels who is the boss

Whenever I wonder about what has been going on in the middle east, I check Juan Cole for the definitive word, and today is no exception:
Rush to Western Strike on Syria slows, but does not Stall | Informed Comment

US intelligence agencies released an intercept on Wednesday showing that after the attack, a ministry of defense official made outraged inquiries from a local commander as to what in the world he had done.
The intercept would be consistent with local Baath chem warfare units routinely mixing a little deadly sarin gas into crowd control gas, killing small numbers of rebels with each deployment, but in this case making an error and getting the mix wrong. Thus, around a thousand were killed instead of dozens. British intelligence seems to have come to a similar conclusion
Apparently there are new, Jordanian-trained, guerrilla forces in Rif Dimashq near the capital that account for the local commanders’ panic and desire to forcefully push them back.
The intercept does not prove that Bashar al-Assad knew about or ordered the chemical weapons attack. It does not, however, disprove that the Baath regime has a systematic policy of low level use of chemical weapons.
It does put paid to the crackpot conspiracy theory, advanced by the regime and the Russians, that the rebels gassed themselves.

So if Syria has been using Sarin gas routinely on its rebels, and then inadvertently used too much, then this is behaviour which the world needs to condemn.
Exactly how is still the question, of course, but the rationale is clearer now.
Oh, and Juan also says that there is not yet international support for missile strikes.   But it was news to me that Syria has been "routinely mixing a little deadline sarin gas into crowd control gas" -- and that's a war crime that demands some response
Or else everyone will start doing this.