WOW! This is a very strange situation and pink_in_the_middle probably has the best suggestion by contacting an avian vet to see if theres anything that can be done.
I am sure you have already asked yourselves this but is there anything in common each time he is feriously thrashed upon? Did he enter the cage too quickly and startle the bird or was he himself maybe in a bad mood therefore the bird sensed it? These lil creatures are pretty damn smart and pick up on nearly everything.
Good Luck resolving this radical behavior and hopefully your husband has NO contact with DamageX
