how frank must one be?
I believe that frankness can never be justified if it hurts the person you are being frank with. Yes, if something needs to be said, there are ways of saying it to take away the sting which is hidden in frankness.
I think the only time 'brutal frankness' can be justified is if there is a positive, warm, loving, fair, just relationship with the person/persons you are being brutally frank with.
There is really no need to blather out everything that comes to your mind, and expect that people around you will see it in the light of the context, or understand that this is your nature, or not take what you are saying to heart, or be forgiving.
There is also a fair chance that your frankness will backfire causing terrible misunderstanding and irreparable damage...
Filter what you have to say through the sieve of tolerance, patience, caring and love....always thinking of the feelings of the other person.