Menander’s Twice a Swindler (Dis Exapaton) describes effects of a well-bred young man’s love for a courtesan:

He has no self-control
And brings disgrace on us, his friends.^

Self-control was a high virtue in classical Greek culture. So too was helping one’s friends. Love for a courtesan thus destroyed the well-bred young man’s good character, as the Greek’s understood it.