It's a no brainer.
when we are young our bones and flesh are developing. risking serious injury can impede this natural development and cause deformation of problems later in life.
Each of us does not have a completed and fully grown physiology until we are the very least in and around the 18 years mark.
In youngsters sports, there is no hard contact in most rule sets that are sanctioned. This is for the reasons stated above.
I don't have issue at all with telling someone who is subjecting an underdeveloped person to percussive or concussive striking that they are more than a couple of cards short of a deck.
Encouragement of it is less severe, but indicative of an underdeveloped mind.
Are people telling me they are ok with risking the health and well being of their child for their own vicarious desires? then i can only say to that person that they need to seriously reassess and re-evaluate their world view.
there are some wrongs that really are quite black and white.
kids will tussle and fight on their own without any of us stepping in and organizing it.