For the most part, temperament is heritable. It's genetic, folks. All the "retraining" in the world won't overcome genetics. It may make the rooster in question leery of the one person who is booting him across the barnyard, but it WILL NOT change his innate temperament. I've done all the techniques proposed by the "experts" and have never found any of them to work on a cockerel who already has his hormones in full swing and is mating the hens.
The Belgian D'Anver rooster is known for aggressive temperament. They cannot truly be retrained. It's in their nature. I've tried, believe me. All you can do is select the least aggressive ones and breed from those. I've had one non-aggressive d'Anver male and if he hadn't had something wrong inside and passed on, I would have kept only him to breed from. Of course, I'm left with my feathered pitbull male in that pen.
Why put up with a human-aggressive rooster when you can have one like my Isaac, who does his duty as he should, and is completely easygoing and friendly? Check out the video in this post for proof of what a rooster can be like:
https://www.backyardchickens.com/t/384349/sdwd/14610#post_8894682
Another video from photobucket: http://s673.photobucket.com/albums/vv95/Mtnviewpoultry/Video Clips/?action=view¤t=DSCN5537.mp4
To clarify, Ike was not handled much as a chick. He comes from a line of Delawares chosen for temperament. Some breeders may not care about that, but 99% of backyard flock owners and a large portion of quality breeders sure do. And many believe a rooster must be aggressive to be a good breeder or to protect the flock, which is completely not true in my experience. You won't find a more prolific breeder than Isaac-even at over 3 1/2 years of age, he handles over 20 hens.
I do not require my roosters to be cuddly, but I do require them to be intelligent enough not to attack the hand that feeds them. My blue Orpington rooster is the sweetest rooster, too, never even a nip his entire almost six years of life. His sons are the same way because he passed that on to them.