But how do you know that your parenting skills and guidelines were not in effect in this situation?
They may be the most nurting people on the planet for all we know.  I agree that parents have HUGE responsibilites for the safety of their children and while you may not agree with the idea of a 12 year old running a 20' drop, Their 12 years of experience of watching this child grow up may have influenced them differently.  Good for your son! I doubt if I will EVER run class V.