In the Service of Social Harmony, Politeness Often Discourages the Expression

In the service of social harmony, politeness often discourages the expression of negative emotions (even if they are felt) and encourages the expression of positive emotions (even if they aren't felt). In what ways is this good for the individual and/or the society? In what ways is it bad? Using what you know about emotion, make a case for and a case against politeness (as it relates to emotional expression).