That is interesting. I've never had that kind of a problem with my girls. I agree with the others though about Cochins. They are known for their very docile nature and sweet personalities.
Are you talking about roosters? Chickens in general will posture, square off, peck and sometimes chase one another. Sometimes they can be bullies but for the most part, they work it out among themselves. It's all a part of establishing their pecking order. With roosters it can be more violent so...