Man, this had some serious Apocalypse Now kind of vibes. M'benga's heart was touched by the darkness of war, and he couldn't let go of it long after the war was over.
Ending was kind of lame, but I think it's also sort-of in line with Pike as a captain - he's a great diplomat and will always side with his officers, almost to a fault. The ending was one of the times where Pike was himself to a fault. Hopefully Star Fleet either somehow calls it out or throws M'benga under the bus for something.