A: That's a myth. It's been years since horses have been used to make glue. Paste, maybe. A cheap brown paste used to wallpaper shanties. Or gruel. But not glue.
But your horse wasn't killed because of what we wanted him to be. He was killed because of what he was. A loser.
There's no rule that says a horse can't play football. And there's no rule that says if he's going to play, he better damn well be good. Things like that are understood.