Need help with dog aggression..

hes never been aggressive towards anyone or anything up until this incident. Ive got no problem culling a dog with people aggression but everyone thats ever been around this dog cant believe he did it. Hes got a very mellow temperment which is the only reason hes still here. I guess i dont share the same opinion as a lot of people on this issue but i want to try to fix him if i can. Like i said before he was even good with my son when he went to the pen right after. the dogs are penned together and generally my bulldog isnt penned. the cur got out of his pen so im sure it was a dominance issue and the cur just didnt bow down (he is the new dog on the yard). Ive had the bulldog out with the others since and theres no problem. Im sure its just a time issue but i was curious if castration would speed the process up.