A proper burger made from 100% horse is awesome, we used to buy the meat from a local butcher, and oh boy, that was some awesome meat, the taste is different from beef and if done properly one of the best things in the world.
But I see where they´re coming from, if its supposed to be beef it really should be beef, especially today with all sorts of allergies, if you dont know what you´re eating you might very well be up the famous creek realising that you left the paddle upstream.