Dear G; Tried to find you...

[The Barrow-Wight]

I don't know if it would be wise to use anything the Mouth of Sauron said as support for an argument. He was an evil man working in the service of the king of liars, so his choice of titles should always be highly suspect at best. It would be probably be unwise to equate his position in any way with that of Elrond, especially since his claim of unassailability went with the ambassador part of his statement.

‘Where such laws hold,’ said Gandalf, ‘it is also the custom for ambassadors to use less insolence.