You could say that one of the main functions of sport is to provide a means of competition by proxy. The ball goes in the net; the finishing line is crossed first. Sometimes the result is sufficiently mechanised to be unambiguous, sometimes the judgement of a specialist is required (e.g. diving, dressage). Boxing however, and the other activities you listed, do without the proxy element, and require direct contact with the potential of injury. In some cases, the contact is sufficiently rarefied and protected against that actual injury is unlikely (fencing, perhaps), but boxing and wrestling, and other sports that allow a knockout in particular, still have the significant possibility of real injury - for no purpose other than to say that you have won by virtue of causing that injury. To my mind this is simply not civilised.
