Get a new Vet - Do NOT neuter your puppy at all, let alone at such an obscenely early age.
It will do nothing for his aggression which from the sound of things, the vet is herself provoking. If the Vet knew Basenjis, actually really KNEW Basenjis and had animal welfare at heart, she would know how to treat a puppy and realise it is showing fear of the unknown, lack of confidence in HER and general unhappiness at the way he is being treated.
Explain to a new vet why you are make the switch. Say that in conditions and circumstances when he is feeling unsure of himself, lacking confidence or uncertain what is happening, he will growl. As when muzzled and being treated like a pariah by an ignoramus. But that at home he is a normal, happy puppy. OK, he nips, but you can cure him of that easily enough.
Do not listen to that Vet - get rid of her, soon as possible. We should soon be allowed to be with our pets at the Vet's again. I hate having to give my two over, although I know the Vets know them well and treat them very kindly.