Wiesel reestablishes his ethos in the conclusion to "The Perils of Indifference" as follows: He reminds the audience of his experience as a Holocaust survivor.
Ethos, or the ethical appeal, means to convince an audience of the author's credibility or character. Wiesel wished to express the idea that indifference is worse than hatred, because it is essentialy an absence of compassion and a lack of acknowledgement.