I don't see how anyone, terrorist organization or soverign state like Iraq, could send chemical or gas weapons to Israel on rockets and not simultaneously decimate the Palestinians who live in and around the Israelis.
The point of WMD is in the word MASS. The weapon has to be able to affect masses of the population to be effective. This means hitting a large territory or at least spreading to a large territory with a mass of population.
Well, if they gave a hoot and a half about the well being of the Palestinians, then I'd see your point. They don't.
The VERY FIRST whiff of chemical attack in Israel, and all bets are off. If the gas came from Iraq, then we'll be playing bumper tanks with Merkavas and Abrahms racing to see who can get to Baghdad first.