With my last roosters the chicks were raised in a free range situation by broody hens and grew up respecting/fearing the flock masters. The pecking order being what it is, there would be periodic scuffles/wars as young birds tried to improve their position.
Well, you have already discovered what the jealous biddies tend to do to crested birds. It happens quite frequently in mixed flocks. Give the integration a try. If it does not work, just get rid of the EE if the Polish is your favorite.