Goliath overreacted yesterday. I took Mean Lady out for pictures, & put her back into the coop, & he attacked her. He stopped once he realized it was a flock member.
It's dark in the coop, so he must've didn't recognize her until she went outside into the light. The flock protection instinct is definitely strong with him which is good, a trait I want, but it'll make introduction of new birds a bit difficult.