I think maybe there are gentle/aggressive birds to every species. I raised cockatiels for many years and I've had some, that even though I hand reared them, grew up to be distrusting of humans and would bite every chance they got, and I had ones that had been raised with little to no human contact, yet once they were tamed they were sweet as could be. I also keep reading that Sebright roos are suppose to be aggressive. I have a little guy named Pip and he is about the sweetest thing on Earth. He is probably the only chicken I have that HASN'T tried to peck me or another chicken. He used to butt chests with my other roos, but it already seems like my Bantam Barred Cochin roo is king of the coop, lol. Poor Pip is like the very bottom roo out there. He seemed heartbroken when I moved him out the coop and when I go out to feed and water them and spend time with them, he sits with me and waits, like I'm suppose to bring him back into the house with me, and when I put him back down he give me this look like I just betrayed him. I eventually want Polishes, and I hope that when I get some, they will be gentle and good as I have heard nothing but good things about them up until now. I hope your boy stays sweet and doesn't cause you problems. Good luck with him!