You sure it's protective? My dog has seen a bunch of "iffy" looking people and doesn't bark and growl. I run a lot with my dog past midnight because I want to play during the day so I see my fair share of iffy people. What was your dog protecting you from? A repair person minding their own business?
I bet your dog would have done the same thing if it was a priest in a nice suit....
The dog sounds territorial if he only does it to people coming to the house. Territorial isn't a bad thing if you can control your dog. If you tell your dog to shut up and he doesn't listen then yeah its a bad thing.