Q: How do I stop my dog from barking non-stop at my guests?
A: If your dog barks non stop at guests, what they're saying is, "hey, I'm uncomfortable with this situation, and I'm letting you know about it" or, "hey, person, pay attention to me, this space is about me, not about you". Both of these are forms of dominance, and therefore need to be addressed rather than just ignored.
When a dog is letting you know that they're uncomfortable with the situation, essentially what they're doing is saying, "hey, I'm in charge of this situation!" Granted, there are exceptions. If your dog does not normally bark at guests or strangers, and then there's that one person that they're barking at non stop, that's the time to listen to their instinct.
But if you want to develop a happy and healthy relationship with your dog, I've found that it's best that your dog knows that YOU are in control of the situation, and NOT them. The dog that continuously barks at guests is simply looking for someone else to lay down a different rule. You need to disagree with this behavior, and make that clearly understood to the dog.
A sharp, "no!" and sending them out of the space will let them know that you disagree with that behavior. Sometimes telling our dogs, "no!" and sending them out of the space can actually create more of a vocal competition between dog and owner where it becomes more of an argument.
If this is the case in your situation, consult a professional immediately because there are more elements at play than just this situation of your dog being uncomfortable with guests. Chances are, they believe they are in control of a lot of other things, too. So you need to consult a professional immediately so they can help you find those things and address them.