How is "this sort of reaction" over the top when someone dies?
I am by no means an expert on horse racing. I don't know the names of the horses and the jockeys, nor do I know about the odds and amount of money at stake. But I know a lot about horses and have first hand experience with former racehorses and know that some are in pain, sometimes even for the rest of their lives, once they retire.
A horse loves to run, but racing and running are two completely different things, and especially so the Grand National which is basically a graveyard for horses. These horses love racing as much as pitbulls love dog fighting. "But yo dawg, this is what he was bred for and he luvs it." feck no, he doesn't. He is fighting for his life, and he is terrified.
This "sport" exists purely because of money and the thrill of it, not for the love of horses. The abuse of racehorses start at conception, being human-bred genetic freaks equal to pugs. They are not naturally healthy horses, and they do not deserve to suffer and die in the name of tradition and betting.