Villagers can sort of defend themselves maybe.

The villagers are strictly pacifists, but the iron golems, not so much. So during a raid the villagers will actually upgrade an iron golem or help out other villagers. The toolsmiths, weaponsmiths, armourer and fletchers could give iron golems a new set of tools to fight back with. The farmers and butchers could give food to injured villagers to heal them.