and by not shutting the dogs in a different room desperately wanting to get to the guest I make the guest at the door into less of an issue.Your right, a dog shut behind a door, may bark and bark some more, it needs to see.
This is where dog gates are invaluable, the dog can see everything, the person at the door can also see you have a dog. The dog is not shut out at all, so answering the front door is no issue as our protectors are still watching and happy with that, they can still wag their tail, or growl if so inclined, these gates also allow visitors to come without some dogs over exuberant greetings. :-P
If anyone isn't who they claim to be and tries anything my dogs are then there ready to help me out :-) Totally agree with what you are saying, unfortunately in our topsy, turvy world now it would most probably end up with you having a law suit.
Just as an example, going back quite a few years ;-) I grew up with two gorgeous Rough Collies their temperaments were second to none, they went everywhere with myself and my brothers all the neighbourhood children could walk up and stroke them infact anyone could approach them, they were well known throughout our village, never on a lead

and very, very, friendly, greeted by all, for an aloof breed they were certainly not as per their natural traits.
One morning, I went to the front door whilst my mum was chatting to the milkman who we'd known for years and our Collies followed me, mum had put my hair in ringlets and the milkman touched my hair saying how pretty I looked, well our male RC went potty, barked and growled and went to bite the milkman, he only missed because the man moved. He had never acted as a guard dog before, but obviously did not like the man touching me.
So who knows what may make anyones dog react, all the man did was touch my hair, imagine if a postman were to tap you on the shoulder, shake your hand, a dog may one day decide to take exception to it, you can never guarantee that they won't, that is a lesson that I learnt.
In this day and age you would be in court. :-(