Yeah, I'm not a real fan of barred rocks either, but this was the first hatch and I kinda just took what I could get.....the Wyandotte and australorp are the real ornery characters.
But, at the end of the day..... any individuals who don't get along with the flock will be shot....
In our experience, chickens become jerks when they're stressed....hot, cold, hungry, thirsty, etc, and definitely when overcrowded, or not getting enough protein in their feed they'll start eating chicken.
Most layer feed is 16% protein. I kinda think that's the bare minimum manufacturers can get by with, I like to feed the 20% stuff, or supplement with "dogfood" meat from the pigs.