Discuss kthrnrm's answer to: How can I train my dog in order to stop him from ...

Aggression does not come in many forms, only one. If you're dog is showing signs of aggression towards others it is not socially trained properly. You need to show the dog who is the master and you ARE the master and responsible for the actions of YOUR dog. If you can't control it's behavior, then the dog needs to be kenneled whenever guests are present, until you become the master and the "Alpha Dog," he will continue to rule the roost. You have to show the dog who is master and who makes the rules. If you allow him to take the lead, you are lost. You need to assert your authority and let him know that his behavior is UNACCEPTABLE, then and only then, will he submit to your commands. As long as you allow him to rule you, you will never win!

YOU are the alpha dog and he has to recognize that fact before he will ever be submissive to your commands.