I believe that sometimes in diplomacy, you have to accept that peaceful negotiations have failed, and let your hired goons take Old Yeller out the back.

We must be vigilant about not shooting first, but in self defence or defence of others against violence, then sometimes it's the only way out.

In order to give these words credence and agree that the hit team was a violence of last resort, wouldn't we need a little more evidence?

Seems more likely that Bin Laden was killed as soon as his whereabouts became known, which would hardly indicate an exhaustion of diplomatic potential.

When it come to violence of last resort, I'm not certain it's ever really possible to satisfy the burden of proving that action is absolutely necessary, and all non-violent methods of resolution have failed and will continue to fail.