I suppose you find this within all breeds...and not just dogs. I know my aunt was advised not have a ginger Persian because they are vicious..by a breeder of other colours :roll:
I count myself lucky to have a golden cocker with a great temperament as he came from an unreliable background, but I would think most reputable breeders turn out solids of sound temperament. It highlights the reasons for going to a good breeder yet again.