Being defamed, we intreat: we are made as the filth of the world, and are the offscouring of all things unto this day.
All this we bear in the opposite to the self-assertive spirit of the world (Matthew 5:39): a tacit reproof to the self-sufficiency of the Corinthians (1 Corinthians 4:8).
Defamed, we entreat - namely, God for our defamers, as Christ enjoined (Matthew 5:10; Matthew 5:44). Or, we reply submissively and deprecatingly.
Filth - the sweepings of a cleaning. Or persons sacrificed for the public good in a national calamity. Christ is the true Katharma, or cleansing expiation.
Of all things - not of the "world" only.