Firstly, human life is undoubtedly precious. If somebody, for example, dies of a dangerous sport; his family would be very upset. This is also a loss to the society considering the fact everybody has to spend twelve years on schooling.
Next, sports are meant to help people improve their health. For instance, playing table tennis should give you a better level of reflection. Hence, there is no need to have life threatening sports.
Moreover, dangerous sports can result in serious injuries. Even though the lives of the people playing this kind of sports can be saved, they still possibly have to suffer from permanent injuries which can make them disabled. Hence, preventing people from this kind of sports can reduce the chances of permanent injuries from sport related accidents.
Finally, a challenging sport needs not be dangerous. It is commonly believed that people like to play dangerous sports because they are considered to be more challenging. However, there are many challenging sports which do not require people to face dangers.
To sum up, I would strongly recommend that dangerous sports should be banned from our societies. Because they do not contribute to the development of human life and because of the dangers people could face, safer sports should be considered as the best alternative.