The original Star Trek series specialized in allegory and moralizing. One of my favorites from the first season is A Taste Of Armageddon, where the crew finds a world executing a peculiar style of war. The wikipedia summary is:
Here is the episode trailer (you can also watch the full episode at youtube):
Captain Kirk is horrified that a society would execute war in such an anesthetized way and that people would willingly report to termination booths. Kirk would argue that war ought to be ugly, painful, and devastating so that we realize its full costs and make efforts to avoid it.
I like the message of this episode. However, I would extend it even further than its writers would likely have intended. I share Kirk's horrors but not just with the institutionalized system of war he finds; I experience this same horror (from time to time) with the institutionalized violence of government itself.
In particular, I find the idea of a justice system, where we institute a cold, legalistic process for judging men and doling out punishments similar to that fictional war system. In both cases, violence is institutionalized in an attempt to do away with its negative effects, but in fact the system only serves to propagate violence further. We make violence clean, dress it up with rituals and icons, and tuck it away as out of sight as possible. The horror is that men view these systems as good and willingly participate in them.