I don't think Mike Tyson was cast in the first film for the specific objective of rehabbing his public image, whereas the casting of Gibson seems to rather cynically reek of it.
Personally, I think stunt celebrity cameo casting is passe anyway, unless it's done very, very cleverly (i.e. NPH in HAROLD AND KUMAR).
I don't think anyone goes to an escapist comedy to see some disgraced public figure making amends.
"Impossible is just a big word thrown around by small men who find it easier to live in the world they've been given than to explore the power they have to change it. Impossible is not a fact. It's an opinion. Impossible is not a declaration. It's a dare. Impossible is potential. Impossible is temporary. Impossible is nothing.”
~ Muhammad Ali
