Simply put, I disagree with you, and you are wrong. Beating an old champion is a regular occurrence in boxing and does not make the guy that does it an ATG.
Sure, you have a right to disagree, but you gave two bad examples. Spinks is an ATG, and Douglas didn't go on to do anything of note, which is not the same as doing as little more, as I said. You are a fine poster and a gent, and I am fine disagreeing with you.