Sentence:  fearful of being mistaken for a <WSD>Jew</WSD> , he seeks protection in his Nazi uniform ; clinging to the enemy Jew idea , he is forced to overcome habits of politeness and neighborliness ; once in power he begins to give vent to a criminal opportunism that causes him to alternate between megalomania and envy of those above him . 
Meaning of the word marked with <WSD> tags:  a person belonging to the worldwide group claiming descent from Jacob (or converted to it) and connected by cultural or religious ties