You never specified what age is deemed to be "young." I am going to assume you are talking about kids under the age of 10. Kids under the age of 10 are still growing and developing, and putting a child in the way of a risk of harming themselves is dangerous because they are so young and still developing. While it is good to be exposed to things at a young age, extreme contact sports for younger kids is dangerous to their well-being. Needless to say, children's decision making is still developing at a young age as well - which may result in more injuries and conflicts during such sports. It is also a proven fact that younger children are more prone to concussions than older and developed children. That is why, the article listed below explains in further detail, doctors recommend the age of 14 to be the age children start to play those kind of sports. Why risk a higher chance of getting a concussion instead of just waiting for it to be safe for the child? While comfortable risk-taking is a skill children need to know, contact sports which have a high chance of putting themselves at negative health risks is definitely not the best way to teach children the concept you expressed in your argument.