From an animal rights point of view, slaughtering horses should be much less a problem than slaughtering pigs or chickens.
Horses are not fatten to be slaughtered as most other animals, but they are used for other reasons (sports, police...), and only some of them are killed (for several reasons) and than slaugthered. They live a longer and probably a little more joyful live.
Exactly.
I also regret the relatively recent outlawing (in those few US states where it wasn't before) cockfighting. Even a fighting cock killed in his first fight has led a many times longer, many times happier life than your fried chicken.
Note: Horse is not "widely" eaten in Germany. But it is available in many regions. And the horse sausages I have had have been very nice, and actually not so very different from Frankfurter Rindswurst.