If you're going to eat meat, why not eat a horse? Is a horse really any more intelligent than a pig or a cow? Maybe it's a bit smarter, but is it MUCH smarter? Is it as smart as, say, a chimpanzee? I don't think so.
Horses are considered to be "beautiful" creatures. Cows and pigs are not. That's what it comes down to. If you eat any meat at all, you're a hypocrite to criticize someone eating a horse. Sure, if you're a vegetarian, then by all means, criticize away. But if you also eat meat, you can't complain it someone eats a horse. Any objection you raise against horse eating could be raised against cow eating. Or pig eating for that matter.
People have been eating horse meat for a long, long time. It's only been relatively recently that people have stopped (mostly because it just wasn't as economical as other meats). If you are a meat eater, I see no reason for you to be against the eating of horses. Horses are not that intelligent. And they are certainly not endangered.
Now, Chimpanzees and Gorillas are much more intelligent than your average animal. They are also endangered. So it's not okay to eat them. Same goes for whales. But horses? They're on the menu.