It also teaches you that what people call psychopathic is mostly just a difference in values.
Plenty of people find it enjoyable/heroic/interesting, so to not include those people within modern society is strange.
Are they truly modern?
"Culture" has this double definition of, on one side, "customs", and in the other as basically a synonym for "art". With extra points for "art" being this abstract thing nobody knows what exactly is, but everybody agrees that -whatever it is- it's "good".
So in Spain there is this national sport in which you take something, no matter how horrible, try to include it in the definition of "culture" and... since "culture is good" -> "thing is good".
Bulls? Yes, I hear you, you are making great logical arguments but... they are "culture" (purposely being ambiguous about whether you refer to "traditional Spanish custom" or "form of art"). And that's it, that's the end of the argument: Bulls == culture == good. Whatever you say, the answer will be "culture". And you are not going to argue culture is bad, are you?
And it's not only bulls. You can use it with whatever you want to support, and somehow in Spain it works quite well!
This is where it falls apart imo. Of course some aspects of various cultures are bad.
They may have relied on "traditional custom" to get here. But they are using "art" when asking "Are you saying culture is bad?". Forget logic, any complaint to bulls is now obviously coming from uneducated idiots. Any "cultured" person will surely agree that culture is good and ergo bulls are good.
What I'm saying is that, at least in Spain, it's common practice to overextend ANY meaning of "culture" to then use the "art" meaning as a joker card in any argument. It's used in bar conversation, and it's used in the Parliament.
All those traditions were created with a purpose: Release social pressure and to signal potential desirable partners with the right skill set for the job. A non trivial issue in our societies. When everybody is a farmer, proving that you can manage bulls moves you up in the social ladder.
But San Fermin is not about bulls, is mostly about booze. Olympic pools of booze melting your social barriers and helping you to mix with the people.
For tourists is about commiting faux pass with less social impact. Nobody will tell your grandma that you never seen a single bull and ended the night snoring in a street corner covered in vomit and with a broken bottle in your hands (Or with luck, wake-up next to a stranger in a much more pleasant way).
And because they made lots of new friends, because being "partners in crime" always make people feel closer.
The sweet money from tourism is a nice bonus, of course, but the social aspects would worth it even without it.