Welcome to the Forum. It sounds as though this 'protectiveness' has been going on a long time. I agree that probably it would be best to get help from a behaviorist but make sure that they have experience of Basenjis. In the meantime keep him away from your guests. It's possible that he's stirred up by the excitement so it's best to try to keep him calm when people are around.
Hello from Limoges, France!
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We'll be picking up our pup born on December 2nd just outside Paris in early February. Elsza will be my first Basenji, but my third dog. My past two dogs were rescues, and my first pup. Both past dogs were rescues and already partially trained. I work from home so will have lots of time to train her. Look forward to reading up on the breed and different tricks from you all.