As for punishment - I'm not particularly keen on giving these guys a hard time. Maybe dock part of their pay for a few months, but the key thing is to give them a good long talk about how stupid their actions were, especially the videotaping part. In fact, the Corps is instituting new "battlefield ethics" training in light of this incident - i'm not sure how seriously they're going to take it, but it's something I suppose.
To be honest, the actions of these Marines upset me, but only slightly. Desecrating dead bodies has been going on for a long time, it doesn't make it right, but its understandable. I'm not OVERLY worked up about it.
Now if we're going to talk about real moral dilemmas in war, let's talk about the use of drop weapons. That's a conundrum if I've ever seen one.