It is not enough to “punish” Assad. The Jihadist would utilize WMD if given the chance.
The Jihadist have hijacked the Free Syrian Army. If we initiate retaliation against Assad At All, we should simultaneously neutralize all known Al Queda/Jihadist units too.
This gives the true Moderate Syrians (the vast bulk of the Free Syrian Army) a fighting chance to overthrow Assad, develop a democratic state and not have sectarian strife as seen in Iraq.
Additionally it would send a strong message to Iran to abandon its quest for nuclear arms.