You've definitely got a point Keith....but the problems are rarely as simple as that when we are talking about retaliation.

If it can be proved that Assad deliberately used nerve gas, some sort of retaliation would be the "right thing to do", but sometimes the right thing to do, is not the "best thing" to do.
Getting rid of Saddam was probably the "right thing to do", but it has not turned out to be the "best thing" for the people of Iraq.

There is nothing simplistic about running these countries or keeping the warring factions from butchering one another.