Just to respond to many of the concerns I have read here. I grew up on a horse farm. We raised Thouroughbreds for racing. As difficult as it may be to believe, most of the horses (which I absolutely love) are treated very well. My family was very selective in choosing our trainers and groomers, and NO abuse was tolerated. I am not saying that abuse doesn't happen, but an ethical horse owner will recognize the problem and shit can the asshole quickly. We did most of the training ourselves as a family, and that may have also helped to prevent there being a problem.
As a side note, it always seemed to us that the horses didn't object to racing. Infact, on race day at post time we could see a change in the horse's mood, they became excited and wide eyed, and almost seemed to enjoy the run. Even on the farm in the off season, our horses were always high strung and wanting to run, they are noble animals, and I couldn't imagine being cruel to them.