On his travels, Diogenes the Cynic came to a stream that was flooded. He stood on the bank, unable to go any farther. One of those ferrymen who regularly carry people across rivers saw that Diogenes did not know what to do so he approached the philosopher, picked him up, and kindly carried him across the water. Diogenes then stood on the opposite shore, bewailing the poverty that prevented him from rewarding the man for his good deed. While Diogenes was still pondering this state of affairs, the ferryman saw another traveller who could not get across, so he ran off to offer his assistance. Diogenes accosted the ferryman and said, 'Well, I do not feel in your debt any longer for the favour that you did me. This is not an act of judgment on your part - it's an addiction!' The story shows that someone who assists both the truly good and those who are undeserving is not seen as a philanthropist, but is instead regarded as a madman.
Source: Aesop's Fables. A new translation by Laura Gibbs. Oxford University Press (World's Classics): Oxford, 2002.