People that breed for it intentionally are being cruel. It's one thing to end up with an unforseen problem or even if there's just a small chance of a problem, but to breed something that WILL get it..mean.
Have you ever seen one of these guys have an "episode"? I had a nice colt that had it, just after they started being aware of HYPP, and he'd have seizures if he got a bite of sweet feed. His eyes would roll back and he'd struggle to breathe, his muscles locked up and he'd fall over and gasp for several minutes. HORRIBLE to watch. I would never breed for intentionally. He was HH, by the way and I had him gelded, of course. The lady that bought him was well aware of his situation and she kept him a long time, but he finally had THE seizure and and died.