The treatment of the bulls during the fight is clearly revolting. That's my sentiment and I'm sticking to it. But what about before the fight? Let's just say it's not much better.
For hours prior to the fight, Bulls are held in a miniscule lockup where they are deprived of food, water, light. All of life’s essentials. This turns the Bull from a quiet and peaceful animal, into the ferocious killing machine that we always associate the creature with.
The animal is just activating it's self-defense mechanism, and because the audience doesn't see this transition, they feel no remorse when the fierce creature is killed.
In fact, often times the Bull is harpooned prior to the fight in an attempt to further agitate them. Then the crowd bears witness as this mangled animal is massacred. Sounds like great sport to me.