Powell is a soldier and -generally speaking- soldiers want to prevent war not wage it. They are, after all, the ones who die.
But the war has been brought to our shores and passions run high. Another atrocity like WTC and it will be hard to stop the planes and missiles.
One thing we could do is not exercise our veto the next time the question of punishing Israel for ignoring the UN sanctions concerning settlments on the West Bank. That would send two clear messages.
1) Israel would learn that we will not back her up if she defies the UN.
2) The Islamic world would learn that we are not willing to be a party to represion.
Then we would have to apply the same even-handed approach to the rest of the world and withdraw support from any regieme we deem opressive.
But to quote Eliza Dolittle, "Not bloody likely!"