It now seems possible that Sarin (or something) has been used by the rebels. So both sides have arguably crossed the 'red line' and we should bomb the lot. Or we could learn the costly lessons of Iraq and Afghanistan, and not assume that military intervention makes everything fine and dandy. Iran backs Assad, the Saudis back the rebels, Israel bombed Assad's weapons research facility, the Turkish army manoeuvres near the border, and Russia makes threatening noises. It's a right bloody mess, by and large, and keeping clear of it is only sensible.