This particular moment in Star Trek is actually quite important. A lot of people don’t realise that understanding something is not the same as approving of something. This particular episode (A Taste of Armageddon) had a civilization where war was fought on computers instead of on the battlefield and instead of people dying in combat they would send the calculated amount of “casualities” into a camp to die. Kirk is outraged completely by this and rightly should be, but Spock is not so overtly disapproving. He understands why they might think their solution is better for their civilization and takes the time to think about why they are doing it. Even though he can understand why, he still believes it is wrong for them to be doing it.
There is a separation between understanding something and approving of something that a lot of people seem to miss.
The scene in the train station where a young boy smiles at Cyclops and he smiles back was unplanned. The boy was a huge X-Men fan, and Cyclops was his favorite. The scene originally called for Cyclops to look at the train schedule, but according to Bryan Singer the boy could not stop smiling at James Marsden. Finally, during one shot, Marsden just looked back at him and smiled, much to the boy’s delight. Bryan Singer liked the idea so much, he kept it in the film