As bad as he is Assad had an on organised army to be responsible for the use of these weapons now its the FSA who we can't trust, Al Quaida probably and I imagine other independent fighters.
When Assad falls the terrorists will refuse to give up their weapons will be better armed than ever.
Who needs to hijack planes when you can fire an anti aircraft missile at it civilian or military?
Assad has created mobile chemical weapons factories if the rebels get their hands on one of them then God help the world
Take a small amount of nerve gas into a shopping mall and the only thing anybody will be buying is body bags, you don't need a missile if your not trying to gas entire cities.