I have partipicated in the run of the bulls, the encierro. Must say that the run of the bulls is really addictive. It's extremely intense and filled with adrenaline. They have done this for thousands of years in spain. I was not all comfortable with curelty during the bullfight, mostly due to coming from a different culture, I think. To me, the run of bulls is okay, because no one is killing bulls, but people are hurt. It's what they do with the bulls after the run, killing them in a ceremony, called bullfighting, that is the nasty part. I am not against or for it, that's something the spanish people have to figure out.
If I had to choose between living as a cow in the states for the beef industry, or beeing raised to become a bull for bullfighting, I would choose the latter. The conditions meat cows are raised in are really horrible compared to bulls for bullfighting, and wonder if people are aware of this when they eat their burger at McDonalds, complaining about the San Fermin festival in pamplona.
A tip, the tomato festival in spain is perhaps a better experience than the San Fermin. Throwing tomatoes at each other is really fun!