Sentence:  If his attack on Christian morality and on other moralities is going to be worth anything he has got to be "right" about the effect of teaching pity and justice — that it merely hides the <WSD>"ressentiment</WSD>" of the weak while it does injury to the strong. 
Meaning of the word marked with <WSD> tags:  A sense of resentment arising from suppressed feelings of envy and hatred, often leading to a frustrated sense of inferiority, with various social repercussions. (from 19th c.)