Well, we should give D his or her space, but that does not mean that the rest of the guests have to open their arms to draw that person in. Life doesn't work that way.   I do agree that it would be unfair of the host to allow others to block the doors if that is not the hosts wish.   It all goes back to the person in charge and what they allow or disallow. This party is being held in a private home, not a public venue. If it were in a public venue, there are other authorities who would be in charge anyway.