I don't see this as true, I have 18 roosters, all raised the same way, all had the same amount of attention. 17 are all big babies. Only 1 is a total butthead, & wants to beat me up all the time.I would not count on a male for 'protecting' the flock in a free range scenario.
Human aggression has much more to do with how the keepers behave than breed.
The human aggression is hereditary amongst roosters, & hens. One of my friendly boys produced an Aggressive hen, so somewhere down the line, there was a human aggressive relative. This would be happening more often if I were to breed my human aggressive rooster, rather then a friendly rooster.