I really doubt neutering influenced any aggression. Usually it works the other way around unless the dog is in some kind of pain possibly from the procedure gone wrong.
If this were my dog, my first instinct would to have him completely checked out medically. If the dog checks out medically then you really should consult a behavior therapist.
It's your dog, you know better than anyone if you think the dog bit someone intentionally. In my personal experience, I have never seen a dog bite anyone unless it was in pain, fearful, or felt threatened. I do know that dogs temperaments can be affected by breeding. Since I do not know the history of your dog, is it possible something happened to it when it was younger that you might not be aware of?
We have taken special care to consistently socialize our Basenji since he was a very tiny puppy. He has gone all kinds of places and met all kinds of people and dogs, and continues to do so, so that he will not forget. We have always touched him everywhere, tugging (gently) on his ears, tail, paws, etc, putting hands in his mouth, rubbing his muzzle, everything. This has resulted in a dog that likes everyone he meets, especially children (which is odd, because we don't have any) and will tolerate almost anything. The only sign of aggression we have ever seen was when a strange man came up out of the woods one day on our walk. The man surprised us all, and Roo gave a low growl of warning.
Does your Basenji bite everyone or is your dog selective? Miranda and I had a rescue Americian Eskimo that was very loving to us, but he was a selective biter, he was very fearful of strangers and just plain out disliked certain people. In fact he tried to bite Miranda's father at one time. Dogs are very protective of their packs. If they associate a behavior or a scent as threat then any dog can become aggressive.
Even though our dog bit someone, we did take time to understand his behavior and then as responsible owners we made sure that this dog was never allowed to be in a situation where he could hurt someone. With proper precautions, he lived a long happy life. He was no trouble, really, we just had to be aware of his issues, and be certain to accommodate them.
Jason and Miranda