If the gander gets too aggressive, its time to train him. I have an Embden fella I have to watch my back with. If BB (Big Boy) decides he wants to bite or flog me, he gets a lesson. I catch his neck first, my other arm goes around the wings and I pin him to the ground. This is the natural way geese communicate dominance in a flock. I hold him down until he stops struggling. I will not tolerate any of my animals attacking me. BB will eat from my hand, and is normally very social. When his goose hens are brooding he will become a real jerk.
I am glad he is outwardly protective of his goose and goslings, but I will also remind him I will not tolerate any aggressive behavior from him, period. They are smarter than folks realize, and can learn where to coop up, and whats not ok socially.
Did something similar last year and he settled down. With the girls laying the closer he gets to the goose house the worse he is. Guess it time for another lesson.