Yes, violence can be acceptable in sports if the particular sport calls for violence. Boxing or Mixed Martial Arts are violent sports, and as such, they require violence to even exist. Indeed, even non-violent sports like American football require violence in the form of tackling, as does hockey with checking.
Some sports are inherently violent. For example, boxing, mixed martial arts, and wrestling are all violent in nature. Getting rid of violence altogether means these sports would no longer exist. Plus, the nature of these sports has always been more about people's athletic abilities and less of a glorification of violence.
No, because it can kill you in a very painfull way. It also can get you very injured. It can also get you suspended from a game or games.Violente nature is bad because you could be outside and the person could hurt a pedestrian. Time is money, so dont waste it