This is a very good question. Is the aggressive behaviour instinctive or learned.
Geese tend to be aggressive because they are protective of their young. This seems to be instinctive (not learned) so this is likely to be genetic. It benefits the survival of geese so it is a trait that has been passed down generations. More study would be required – involving genetics, but also study of behaviour.
They aren’t really scared of people because they don’t see people as a threat. Often they have been fed by people. This is behavioural.