No one here is saying kill aggressive geese, we love all our geese. But saying geese HAVE to be aggressive and saying it's acceptable for them to chase adults and children? You're out of your mind. Many dogs were bred to be aggressive to people, "guard dogs", but if they bite someone they are put down, what's your argument for that? Just let them? Because they were bred to bite strangers?
Sure in some cases "training" geese doesn't help, but my gander would never DARE come after me.
Put up a sign the same way people do for guard dogs or wet floors. If you warn them and they get bit then that is their problem because they were stupid enough to disobey the posted sign. Also keep them locked up in a fenced in area so nobody can get to them so you wont have to worry about people getting bit.