Jimmy clearly showed that he had trouble with killing his old friend. I think he still kind of liked him too much. So I don't think Jimmy was giving him a kiss of death, he was actually trying to save him by making him look in the direction of where the assassin would come from. This way, he wouldn't lose face by canceling the hit, but still trying to prevent it from succeeding.
Jimmy's quote just showed he is not yet ready to be a leader. He gave in to the demands/wishes of the others despite having his own personal idea on how Nucky should be handled.
Jimmy was basically rationalizing that he followed his mother's advice....be decisive .... if you LOOK strong, you will be strong.
