A family and its pet dog function as a unit. The dog has a place in the pecking order, it has its privileges and it has its duties. For example, when there is a big gathering and strangers come, the dog has to vet (no pun intended) the strangers and protect the babies. This is on top of its usual watchdog and dropped-food duties.

A dog which is used to being with the family will whine if put in a room or bark nonstop if put outside. It doesn't understand what it has done wrong. Believe me, nobody wants to hear a dog barking for several hours.

Frankly, Michaelr, your statement that the dog has shown aggressive behavior is not very convincing. I suggest that when you enter the house, you have a little treat for the dog in your pocket. At the door, let the dog see you and its owners being calm and friendly. Say "Hello puppy", offer the treat, and then ignore him.

Do not stare at the dog, watching for signs of an attack. Dogs consider staring an act of aggression.
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I read a book by a vet, and he said that some dogs play a game called "I hate guests." A dog which is aggressive to a guest (growling or barking) should be put in a room for little while, then allowed back. If the aggression recurs, the dog goes back in the room. A dog hates to be excluded from a party, and in a few times, he will figure it out.