What does Dr.Branom quote from the "poet-prisoner?" What is he talking about? Why is he pleased about this?

The quote that Dr. Branom uses is that every man kills the thing that he loves. He means that now Alex's love of music has been ruined by the use of his favorite music during his treatment. He is pleased about this because it adds an element of true punishment to Alex's treatment, and therefore the Governor, who thinks that the treatment is too soft on Alex, will also be pleased.