Guess they can't ask for 'before' and 'after' pics.
As for impotence... it's all psychosomatic. If you believe strongly enough that a sorcerer made you unable to perform, then that's what will happen. Is it really the sorcerer's fault or yours for believing in such stupidity? It's the same reason why chronic pain sufferers are miraculously 'cured' at evangelical churches that do faith healing. Belief that it will work.