Neutered males aggressive towards intact males?

It's not a common phenomenon but it does happen. In my experience, the dog involved was neutered at 6 months or earlier, before ual maturity and probably had aggressive tendencies to begin with due to temperament, lack of socialization or genetic predisposition. Since true aggressive problems usually show up in male dogs around 9-12 months and continue to get worse as the dog ages, people tend to blame the neutering and not the fact the dog had issues to begin with. Since neutering sometimes helps with dog aggression problems but not always, they end up with a dog with aggression problems that would have had them anyway even if left intact.