Really human aggressive cockerels or cockbirds won't give up, regardless of 'correction' methods; they seem to be hardwired to be jerks. A few boys will be able to learn politeness, and that's great. Better yet, a cockerel who never thinks bad thoughts at all!
I've had one rooster, and as many as six at a time, and I think it's individual behavior that matters. Mine aren't made into pets, or hand fed, or cuddled. They are expected to be polite regardless of my apparel, what I'm carrying, or which hen I'm handling. They are not to injure any pullets, chicks, or hens.
In spring, if spats between breeding roosters happen, one or more will be rehomed. I have three breeding groups, so it works out well here with only three or four roosters.
I'd hate to have chickens without also having a rooster, or three.
Mary