There was no 'other' option in this poll so I didn't vote.
I do not think horse-racing is cruel. It's a sport developed to take advantage of the natural inclination of horses to run in herds - that is what they're designed to do - and breeding has made horses that are good for long distance running - thoroughbred types - and explosive sprinting - quarter horse types.
I do not think that quirting in the way jockeys currently use them in the U.S. is cruel. In the Preakness, yes, the horse was probably so pumped full of adrenalin that it hardly felt the quirt. If you watch, jockeys don't often quirt their horses until it's absolutely necessary to get them to react. You do it too often, the horses get used to it and no longer react. It's used to get the horse to react. I remember reading about one famous race - final leg of the Triple Crown, forgot what year - between Alydar and Affirmed. These two horses were well-matched and always slugged it out neck and neck throughout every race they were in together. Affirmed had won two of the three races of the Crown. In the Belmont, the jockeys were quirting them during the final stretch, but Alydar finally got a nose ahead. The jockey on Affirmed, who had been quirting him right-handed, switched to left-handed. And it worked. Affirmed was not used to getting quirted left-handed and reacted by pushing that much harder and won the race.
Quirting can range from a stinging sensation to real pain but remember a thoroughbred horse can weigh up to half a ton. A 90lb little man quirting him in the final stretch of a race is unlikely to do anything more than irritate him.
But what I think is cruel, is racing these horses so young. They should wait until the horse is at least 5 years old before racing him, the same with quarter horses, so that their leg bones get stronger and their muscles more developed and they're mature.
However, horse-racing has always been the realm of rich people because raising horses is extremely expensive. They're animals that do not give anything to humans and require tons of food and a lot of health care. In the U.S. we don't eat them, they do not give milk or fur and most importantly we no longer use them for draft purposes, so there is no real reason to raise them anymore. However we do use them in sport and the quicker they earn their keep, the better. Hence the trend to race them younger and younger, so their owners can get a return on their invested capital sooner.
Any time animals become a commodity, cruelty becomes involved when people care more about their money than the animal.