Ich sag mal so.
Dein Hund ist ein Rüde, er ist unkastriert, er ist in das geschlechtsreife Alter gekommen und er hat ganz schön viel Terrierblut in sich, da ist es nicht unbedingt verwunderlich wenn er gegen männliche Artgenosse aggressiv wird.
Zitate:" A Bull Terrier should not be kept with another dog of the same S.ex, and cats may or may not be safe."
"With other dogs however the Bull terrier can be very dog aggressive if not socialized at a young age. Male Bull terriers that are intact are the most aggressive and are not recommended for homes with other intact males or even neutered males of dominant types of breeds."
"Seeing that they were bred as fighting dogs it is no surprise that they can be quite hostile when other dogs are concerned, especially if that other dog is intruding into the Bull Terrier’s territory...Male Bull Terriers are not particularly well suited to living with other male dogs, especially if they are not neutered."
"Some dog breeds, such as the bull terrier, are naturally more inclined to exhibit aggression toward other dogs and should be carefully monitored in their interactions with other dogs."
"When it comes to other animals, caution should be the byword. Bull Terriers have a strong prey instinct and can cause injury or death to other animals, especially cats. That said, puppies brought up or socialised with cats and other animals can get on well with the animals they know; they can never be completely trusted with other animals. With other dogs, males may not get along with other male dogs. Introducing a Bull Terrier of the same gender as the dog in residence is considered unwise, and some Bull Terriers won't countenance any other dogs, of either gender ."
"they can be extremely aggressive with other dogs. Unaltered males may not get along with other male dogs."