I agree, in this case, the leader was completely at fault for not making sure his boys were prepared both with proper gear and physically. The 20 mile goal was unrealistic and unreasonable for many of the boys, it was their first hike.
This is just where my head goes when I hear of people plowing ahead and leaving others to catch up later, it scares me. This says to me that MAYBE the goal is not reasonable at that point in time. Not saying that the one diggin in their heals refusing to move forward isn't just been a 3 year old thowing a temper tantrum on the floor.