It isn't only racing,it's most contact sports.(Todays racing is a contact sport)

Hockey fans cheer fights,soccer games have the hoodlums,some football fans throw batteries(or baggies of urine) and cheer when opposing players are hurt(Or boo if Santa is on the field) Some stadiums have jails in them to hold the idiots.

Some people at races cheer crashes.

As far as whats wrong with society today; it isn't only today. People have forgotten about the public hangings, the lions and the christians and an early form of wheeled racing: The Chariot Races. All where notoriously bloody and all where heavily attended.

It is what it is. The most basic spectator of anything isn't a fan(fanatic) of what they are watching, they just thought that is where they should be at that moment. They don't really care about the whos and whats, they just want some form of diversion.

Sort of like how it's funny when someone else bumps their head, falls down, or hurts themselves in some fashion. Without testicals, Americas funniest home videos wouldn't have been that funny.