That is not at all why he’s countersuing her. Not even close. Contributory negligence is part (just a part) of his DEFENSE against her claim.
His counterclaim is bringing a cause of action AGAINST HER, alleging injuries, damages, and losses as a result of HER actions.
And, again, SGF doesn’t have a counterclaim claim against anyone. They have a cross claim against MB, saying they have a “hold harmless ” contract with him.