@spec, i think it wasn't what don's son said so much as it was the time of his life when he heard it. i like that it felt completely random, like the way emotions can sometimes pop up on you without making very much sense.
I like the episode. I did however feel like the MLK-ness of it felt like they rushed the writing. We all knew the episode was coming. It kind of felt like they were in the writers room saying "OK, it's the MLK episode, let's get this over with..."