Hi,
It's horrible to see anything being bullied like that, geese seem to be funny about who they like and who they don't.
If you could keep them separate, could you not pair him up with one of the other geese you have, as they should be quite happy kept in pairs, you may have to swap the geese around to see which one likes him best.
Unless someone is looking for an embden gander, he could be quite difficult to rehome.
Good luck,
Regards
Sue