I think it would be poor etiquette even to read someone else letters regardless if they are rude or not. I would hate someone other than myself opening up letters.
Its unfortunate that the person wants to be seen in such bad-light in the first place, but its that person's prerogative and nothing anyone can do about it
Its unfortunate that the person wants to be seen in such bad-light in the first place, but its that person's prerogative and nothing anyone can do about it