I don't want to see all the feral equines extirpated. My gut feeling is that the habitat can support some populations of feral equines, so long as they're kept in check by culling programs or through regular adoption programs. I agree, and would like to point at that the most cost effective "culling programs" are known as "hunting season". The state issues a limited number of licenses for for specific types of large game animals, and the hunters pay the state for the privilege of thinning the herds. There is no reason that this would not work perfectly well with feral horses.
Yep. You're preaching to the choir. "Wild" horse numbers could be effectively controlled that way -- except for the bane of political correctness. Deer, elk, turkey, quail, dove, etc., are politically correct to hunt, but horses? I'm afraid that the horse, like the dog and the cat, is truly a beloved animal in North America. I just can't imagine any scenario that would legitimize a legal hunt on such a creature.
But you're quite right. Their numbers MUST be controlled. But what hunter wants to return home to his wife with his dead "trophy" horse?