I had this problem when I was a dog walker, I used to walk a black lab, 8 yr old, he was a big softie, anyway one day out on a walk a staffie attacked him quite badly and after that he wanted to fight every dog he met it completely changed his character, I suggested to his owners that they should think about getting him neutered and take him to training classes which they did and within a couple of months he was back to his old self again. So personally I would go for it, the operation is quite simple with male dogs and after all if you're not going to breed from him he doesn't really need his b@lls!!