I'm afraid racing, whether it be horses or dogs, is a business and the outfall is excessive breeding and the destruction of the 'excess' is part of the scene. To be honest, animals are slaughtered in their millions to suit our ways, what about the cows, sheep and chickens who all have nasty short lives followed by unpleasant slaughter.
Back to horses, whips are now heavily prohibited in their usage in racing. The kind of horses used in racing are thoroughbred, they have been bred to race for generations and are highly strung and to race is natural for them. Horses are flight animals, running is what evolution has created them for. Whether they like running with a ham-fisted human on top is a good question. I think it's sad that animals are so abused by humans, all mammals share our nervous system and emotional range, they feel pain, fear and social bonds. Just like us.