There were those set on pushing forward their own particular set of ideals. Paul is trying to teach the boasting members of the Corinthian fellowship that chairt is always modest, as Christ was modest. True charity is happy to serve even without reward. Some of the Corinthians were arrogant, full of themselves. Verse five begins with this fourth danger, directly tied into the third, and if only the Corinthians would learn to be charitable toward one another, they would be rid of their arrogance and its accompanying rudeness.
Selfishness is the opposite of charitable love.
The opposite of selfishness is not despising oneself, but love. By not being provoked, the Christians at Corinth might suppress the evil that others might bring out in them. Neither is charity happy when someone does wrong. Whoever is not provoked by others, doesn't think on the evil in them, and does not rejoice in the unrighteousness of others, will find their perception of the truth enchanced. When the truth shines, love rejoices.