Amazingly, Kid is doing more damage to BM than Law. Even if it doesn't make sense, that's what Oda wants to portray
if queen's brachio snakeus coil attack can defeat "armament haki masters" via sheer force, kid's attacks are a thousand times that. hes hitting her with the mass of a fleet of ships with every slam. when the damage numbers are this high even being able to block it with haki doesnt matter. you're still feeling it