Maybe some are imprinting due to be handled, hand fed and petted as chicks? This article has a paragraph about male birds....
http://www.usask.ca/wcvm/herdmed/applied-ethology/Bottle-raised%20males%20can%20be%20very%20dangerous.pdf
After reading about that topic so often here on BYC, I've noticed most of the posts involve young males that were handled or hand fed as chicks, folks describing them as affectionate, gentle, babies, etc. that turned to attacking their owners upon sexual maturity. I have to wonder if a lot of it was a result of that early imprinting and resulting confusion. Maybe some cockerels are more prone to imprinting than others which could explain the varied results you are showing. It would be worthy of an experiment on deliberately ignoring male chicks during the formative months, no handling or hand feeding, etc to see if that tends to continue or if it's truly a line or breed issue.