While I think that the very ending of the episode was too "chummy". (it could've used some somber music) when you watch the show in detail there is a lot dealt with.
1) Kirk kneeling over the crewwoman's crushed, dusty remains and the look on his face.
2) The fact that Kirk was responsible for the death of the woman. It was his planned escape attempt that led Rojan to kill her. Rojan himself said he was doing this because it was obvious Kirk would feel the pain and responsibility of losing one of his people more than something happening to hmself. Rojan in fact says that he and Kirk are alike in that respect.
3) Kirk slamming his fist down when McCoy says he saw the Kelvins reduce a bunch of his doctors and nurses to those little cubes "They've reduced the whole crew!!"