Many chicken people underestimate and even ignore the effect of their own human behavior on young cockerels and older roosters. It's a very significant factor, I firmly believe.
I arrived at this from my own experience. My first rooster, a SLW, was very aggressive toward me and other humans that would stop by. I was just getting started with my flock, this roo being one of the first chicks i had raised. I had just joined BYC and the advice on handling aggressive roosters was not the most helpful at that point.
The roo would run up to me and attack me from behind, ambushing me at every opportunity. In turn, I would do little more than to get up and run him off. The only thing that was accomplished was for both of us to get plenty of aerobic exercise.
My second rooster was a Buff Brahma. He was not aggressive like the first one, but he developed a serious biting problem and would literally drill my hand with his beak when ever I got near him. On BYC at that time was a member called olychickenguy from Olympia WA. He was very intuitive about the behavior of roosters as he ran a rooster rescue and had at least a dozen roos at any given time. He taught me a lot about rooster behavior and the psychology behind it which I credit for what I now know and understand about them.
He tutored me for nearly a year to rehabilitate this rooster, and the rooster finally stopped biting and became a gentleman. Most of the rehabilitation was me changing my behavior around him. I understood how I was always in a rush, made abrupt movements when in close proximity to him, and when I moderated my behavior, the rooster changed his.
Subsequently, all of the roosters I had after him were very well behaved partly due to being gentle breeds, but also my behavior has become much more moderated and self confident. I wrote an article about this.
https://www.backyardchickens.com/articles/i-think-i-have-a-cockerel-now-what-do-i-do.76274/
