This retardness is nowhere near the same thing as Sanji's body being shown to be severely weaker than normal. Sanji's pain isn't theoretical, it isn't assumed, it was explicitly shown. He had it when he fought Vergo. The pain is given in the manga, so it happened.
You must be registered for see images
You can point out Usopp being fine all you want, but it will never change the fact that Oda took the time to draw panels all dedicated to how badly damaged Sanji's body was. It won't change that we have never seen Vergo fight Sanji while Sanji was at 100%, which invalidates whatever powerscaling or feats Vergo "accomplished" during the fight.