1) Its been made clear that Israel is not 100% sure which "group" was involved in the attack, so it would be a broad operation against known groups. This would cause even more splintering. 2) Anything close to Cast Lead would mobilize the Arab world like never before, something which may happen soon anyway. 3) Israel's supporters abroad would be further isolated from the mainstream, and the demise of blind support for Israel, close as it is, would be even closer. etc etc etc A person could go on and on.
U.S. Democratic Senator Merkley airs support for Iran nuclear deal (Reuters)