Western assumptions

From Adam:  "In order to rebut the claim that the rebel groups wouldn't have had access to chemical weapons, sarin gas in this case, all we need to do is remind (or inform if they are particularly ignorant) them that Turkey found sarin gas in the home of some Nusra Front members in southern Turkey.  Why in the world would it be safe to assume they didn't have access to or possession of more, AND it wasn't used near Damascus by someone connected to them? 

Wouldn't this be worth considering before launching the missles?  I guess that depends on a person's goal, doesn't it?"