1) Has any of the Assad regimes chemical weapons been compromised and passed into the hands of the rebels ? ( Can we have high confidence that this hasn't happened ?)
2) Who used the chemical weapons in Damascus ? ( And how do we know ?)
Now there's an argument that if you manufactured the weapons you are responsible for their use, even by your enemies. But that's not the line we are being sold.
Its noticeable how Blairite the bomb Syria govt campaign is - not just in terms of the evidence but also in the way the public discourse is distracted from the key questions.