If he is dog aggressive now, don't expect neutering to help it. Dog aggression cannot be trained out.. it can only be managed. We had a boxer at the shelter got in a dog fight with another dog before he came to us and he was really dog aggressive he got a home with no other pets. Just don't leave him unsupervised with your other dogs since he is dog aggressive. No dog parks either since you know he is dog aggressive just play dates with dogs he already knows.