I think I may have a solution but wanted to get the opinions of some I-doggers...
Whenever someone comes over to our house that Prince doesn't know, he goes into vicious guard dog mode. Now I know he is a Doberman and they are protective to begin with but lately it keeps getting worse and worse. Hackles raise, extreme barking (imagine a "hold" bark in Schutzhund)
He has done this with my grandpa (he has only met him once), my brother (only met a couple of times) and my in-laws(never met). My father in law is staying with us today through Wed. This morning he stopped by to drop off his lunch - Prince was outside at the time so didn't see or hear him. After he left, I let Prince back inside. Well he smelled someone that he didn't recognize and instantly went into his "guard" phase. I got him to focus on me and placed him in a sit until he calmed down. I then led him to my father in laws bedroom and let him smell his belongings. He barked a few times but did calm down...but he was still on edge.
Now what to do about when the father in law comes back after work. I don't know if Prince will remember him since it has been a few months since he last saw him. I planned on having FIL come up and knock on the door, us answering it first and then have Prince greet him. We practice a strict NILF regiment with Prince (since day one) so I don't think its about him thinking he is dominate and showing he is the one who determines who enters the house. I just think he is protective of his home, now that he knows it is his. When I take him out in public, he is fine with strangers and loves all the attention he can get.
Maybe its just men that he has a problem with, or certain types of men. Or he is just doing what Dobermans do when someone enters their property unexpected. He is fine after we tell him its ok and the person pets him - then he turns back into the big baby that he is. I just don't want our visitors to have a heart attack when an 85lb doberman is barking at them. I don't want to keep him confined or give corrections when he acts this way, as that may lead to more serious issues. I know he is protecting, that is what he was bred to do - I guess I am just looking for any advice on this situation.