In many areas, there is no public transportation and a car is necessary to live and work. Economy cars are a necessity in those areas. Horses aren't a necessity to anyone in North America unless you're using them for work (a small minority of the horse population these days), they're a luxury item. Also, broken down and unwanted cars don't starve. They don't suffer pain and fear. It's just not a valid comparison.

I'm not rich. I'm in the category of horse lovers who hope to someday be able to afford a horse, and I appreciate the fact that I may not have to pay an arm and a leg to buy one when I get to that point, but if I had to trade my chance to someday own a horse for the disappearance of the unwanted BYB horse, I'd take a life of admiring the horse from afar. Willingness to condemn thousands of horses to a lifetime of suffering just so that you can fulfill your personal desire to own one is incredibly selfish.

(I'm not following that other forum, but if you feel the urge to repost this there, feel free)
http://www.boxerworld.com/rescue/excuses/