I don't think there's anything inherently wrong with horse racing... horses have been raced informally more or less since they were domesticated. Horse shows, dog shows, dog sports, cat shows, any domestic animal show or sport is all based on entertainment and breeders' pride in the animals they've created and trained. As long as the animals are taken care of, I don't personally see a problem with this, and any accidents that occur are generally just that, accidents. Dog fighting is in a totally different category, as there the animals are *guaranteed* to be hurt, most often very severely/fatally, and that is unconscionable.
Horse racing could be fine if a few things improved.... I do think that the sport can be made a WHOLE lot safer, that breeding can be improved, and that they should race the horses a lot older than they currently do- most non-racing trainers don't put horses under saddle AT ALL until AT LEAST 4 years old, when their bones are more settled. I don't really see that happening, unfortunately (too much greed) and that's why I'm off horse racing for good.