I think that the risks involved with Bullfighting are acceptable for humans. It is a traditional thing, not that it makes it any better or safer. But if people are aware of the dangers of bullfighting then there is no reason that they cannot participate. People are going to do what they are going to do and a rule outlawing bullfighting would not be good.
I understand bull fighting to have a great deal of social value in those cultures in which it is popular. Spectators and bull fighters alike actively make the choice to reap this value from their engagement in these types of events, and I would argue that their awareness of the risk implies their acceptance of it. For example, spectators choose to be entertained at the small risk of being injured. Furthermore, bull fighters and event workers choose compensation and prestige at the risk of being injured. If anything, I would argue that the risk to the bulls is unacceptable on a much higher level than the risk to humans.