It's good to be direct with someone who upset you.
Bill and his friend Bob get into an argument after Bob said something rude to Bill's sister.
Bill wants to move past the transgression.
Bill lets Bob know that what he said is not OK and that if they are to remain friends that cannot happen again.
Bill does not say anything to Bob about the transgression and let's Bob get away with it.
Bill settles the problem with Bob, and they put it behind them.
Bill builds resentment towards Bob and their friendship deteriorates.