Should we intervene in India or for some other Democracy or civilized society which is under attack from militant Islam... good question.
Iraq launches a scud at Israel. Missile defense systems shoot it down. It is quickly determined that it had a WMD payload. Should Israel nuke Bagdad at that point?
I think they need to make this clear ahead of time, and follow through on it.
Further, what about a detected incoming missile - should Israel "launch on warning"?