Fair point Peter.
We are already seeing civilians slaughtered by conventional weapons, so what is the difference?

There is now a perception that a regime that takes that extra step will suffer a consequence.
If that perception is lost, it will not be a world changer, but the world will be a worse place.

Stringy, there is already an "an all out civil war in Syria" even worse than the one in Iraq.
Where have you been?

And, the UN is not weak, it is blocked from any action against Assad by Russia and China.
How could we "strengthen" it?