The "wild horses" of the American West are not native critters. They are the offspring of escapes and abandoned domestic horses, same as with the burros. To be blunt, those who want to "save" them are sentimentalists and not environmentalists.
I see no reason to protect them. You can argue that the same goes for cattle, but the plains historically had their own cattle: Bison by the millions.
The battle over wild horses - Ranchers and animal advocates finally made peace. But critics call it a betrayal.