I don't find this punishment rises to the level of cruelty... over the top, maybe.. but not cruelty or abuse.
instead of forced marches ( not that 3 miles in under 2 hours is tough by any stretch of the imagination).. I chose push ups, crunches, mountain climbers, and bends and thrusts as negative reinforcements
throwing his father in jail and preventing ( chilling effect) him from raising he child with discipline is far more harmful to this kid than having him walk 3 miles with a rock.
at least the guy is instilling some discipline in his child... altogether too many parents can't be bothered to do even that, which results in their child gaining entrance into the throngs of young adults who are complete and utter assholes.
"Judge a man by his questions rather than his answers" - Voltaire
"There is nothing noble in being superior to your fellow men. True nobility lies in being superior to your former self" -Hemingway