It's safe to say we know now why Shinta isn't a soldier. Which is cool, of course, because times are good when people who don't want to be soldiers don't need to be. He's looking at this like it was a scene between police officers and criminals, not between soldiers during a war.

Though Itami is a relaxed fellow, but in addition to what I said earlier about choosing the psycho woman, maybe he was also even more smart and could possibly foresee the possibility of something like this happening on a deeper level. The king already prophesied valuing human life so much will bring the Japanese side problems. Now Itami did show that valuing human life in general doesn't necessarily mean they aren't ready to do what needs to be done. It would lead to even more loss of lives if the king/prince don't get this message and again try to attack in vain, thinking the Japanese don't have what it takes.