Sentence:  It is taken for granted that a beggar does not 'earn' his living, as a bricklayer or a literary critic 'earns' his. He is a mere social <WSD>excrescence</WSD>, tolerated because we live in a humane age, but essentially despicable. 
Meaning of the word marked with <WSD> tags:  Something, usually abnormal, which grows out of something else.