You can't get a horse out of a Minecart like other mobs

If you get a Horse into a Minecart, you can't get it back out like you can other mobs. I think the Horse's hitbox is slightly bigger than the Minecart's, so trying to hit the cart only punches the horse in the knees. You have to actually get on top of the horse, then look down and punch the cart while on the horse.