Many people believe that violent sport is cathartic. There is good evidence that they are wrong.
The commonsense view is that it is good, especially for boys and adolescent males, to participate in violent sports such as football, boxing, rugby, North American hockey, and mixed martial arts. The reason is that it gives them a way to release or vent their pent up aggression through acts of controlled violence in organized sport. The idea is that it is better that they do it in such relatively harmless ways.
But, in their new book, philosophers of sport Mark Holowchak and Heather Reid point out that while "the data are not unambiguous, current research indicates strongly that exposure to aggression leads not to catharsis, but rather to heightened aggression" (p. 87). According to the authors, this poses a major obstacle to reforming contemporary sports, which are largely driven by martial abilities and market forces. Rather than sublimating violent behavior, the evidence, when examined carefully, shows that exposure to aggressive behavior leads to heightened aggression or more frequent aggression. This means we should reconsider our devotion to the sports mentioned above, because by "...condoning aggression in sport, we contribute to aggression and violence in society" (p. 92).
As a fan of many of the aforementioned sports, I am reluctantly willing to reconsider my love for them. Many of them are inherently violent, but to a certain degree I don't think that is necessarily wrong. This is not an issue I've examined, so I don't have a settled view on the matter, but the evidence does at least at least give us reason to question the commonsense view that we can minimize violence by channelling it into sports.
My view is that the positive effects of football, for example, on young males is not the alleged catharsis, but rather the qualities that a good coach requires of his or her team: discipline, cooperation, perseverance, and courage. A sound approach to sports would emphasize these traits, rather than seeking to sensationalize and profit from sport by promoting and supporting violence.