I'm new to these forums so I hope that no one minds if I throw my two cents at the kitty
My dog is very protective of the house and the family. He's usually very wary, and sometimes outright hostile, towards any strange men that come into or onto what he considers "his" property. (Akita/Chow mix and I've heard very similar things about this from other Akita and Chow owners)
But, I've noticed a few things:
1. The more the guy acts like he belongs, the quicker Chewie (my dog named for the fact that he ate an entire chair the day we got him) will relax and go back to trying to herd the cat.
2. The more I show friendliness and gregariousness towards any guy that comes into the house, the quicker Chewie goes back to herding the cat.
3. The more the guy pays attention to the dog, such as trying to make friends, the more Chewie will try to herd him out the door.
4. The more the guy ignores Chewie and goes about his business (fixing a plate of food at a party or repairing the fridge), the quicker Chewie goes back to herding the cat.
5. The more I try to keep Chewie back from herding the guy out the door, the more interested Chewie is in herding the guy out the door.
6. Eventually, Chewie will stop with his protective behavior and go back to herding the cat but it can sometimes take a while.
I haven't tried the treats thing. Perhaps I'll start keeping a box of treats outside the door every time we have company and ask them to give the dog a treat when they enter.
There was one exception to the above behavior. The husband of my wife's friend came to pick her up at the end of a Pampered Chef Party. He walked in, shook my hand, and stood in the middle of the living room while the dog made an effort at looking threatening and staying in between us. Without looking at Chewie, he took a knee gave him a good back rubbing. To my utter surprise, Chewie went from fur up to on his back with his belly exposed in less than a second.
I don't know what that means, but I think that the more nervous you are and the more nervous the man is, the more the dog will try to protect you and the "pack". If you act like everything is normal and the man acts like he belongs, the dog will accept him as a member of the pack that much quicker.