The modern version of small dinosaurs.All of my OEGB roosters and cockerels have been raised together. I've seen some minor 'sparring' between the young males, but nothing that results in injury. They all appear to get along and don't even get in confrontations with one another over hens. Not one has ever shown human aggression and all are from cross bred bantam farm stock that are primarily OEGB. I've seen the main sire that they were originally bred from and he is a beautiful black OEGB down to his dubbed comb and wattles.
It appears that these young males (Feb hatch and younger) banded together in order to 'deal' with larger and more physically powerful birds that just one bird couldn't possibly defeat in a confrontation.
It's pretty impressive to see a big Welsummer/Buff O cross rooster trying to outrun not one but 5 OEGB cockerels who are chasing him down with the intent of doing him bodily harm.
I too have culled roosters for human aggression and yep, expect OEGBs to be scrappy little demons. I just haven't read of them forming alliances in order to take over a flock of hens.