One can be isolationist without being anti-Israel. Paul is anti-Israel. He has made his distaste for that country plain on numerous occasions.
This anti-Israel philosophy doesn't so much come from isolationism or libertarianism, but European style rightism, which is abundant among "palaeoconservatives," whether libertarian or statist.
Given today's geopolitical alignment, it's just about impossible to be an American isolationist without risking the security and existence of Israel - as well as several other American allies.