As far as I can see there are only two positions that are morally defensible.
1. Zero intervention beyond humanitarian aid - Its Syria's civil war after all so lets just stay out of it.
2. Direct intervention - If Assad's regime is evil and needs to be removed then we pick a side and actively intervene - boots on the ground.
Option 2 would be an absolute disaster. Our recent adventure in Libya doesn't bear comparison - Syria has a much better equipped military and doesn't have a handy coastline to park an aircraft carrier off of. Direct intervention would also likely widen the conflict to Lebanon and Iran.
So that leaves us Option 1
A halfway house of supplying arms to rebels is a horrible compromise. It solves nothing and just creates a level killing field. Given that Saudi and Qatar seem keen on supplying arms anyway why does the West even want to be involved? Is it a purely political ploy to spite Russia? The Russians won't want to appear soft and will just supply more sophisticated weapons to the Syrians. Escalation of the conflict will become more and more likely.
It looks like a game of realpolitk being played out with the lives of Syrians. We should have no part in it