The key word is "legitimate self defense".
8) urges that, if the Government of Israel is compelled to take military action in legitimate self-defense against Iran's nuclear weapons program, the United States Government should stand with Israel and provide, in accordance with United States law and the constitutional responsibility of Congress to authorize the use of military force, diplomatic, military, and economic support to the Government of Israel in its defense of its territory, people, and existence.
Rand would have to beleive it's "legitament" to vote for military force.
SEC. 2. RULES OF CONSTRUCTION.
Nothing in this resolution shall be construed as an authorization for the use of force or a declaration of war.
This means that the resolution in no ways authorizes military force. The whole resolution is merely stating that we would stand by Israel in the event she needed to defend herself. They would still need to vote on its legitimacy to use military force.
Don't forget...in "their" world, Israel is our ally. What would a lone no vote on this resolution have gotten him?