Before deportation, Moshe was well liked and no one objected to his presence. He was kind, gentle, and had dancing eyes. He was a teacher to Elie.
After the deportation and Moshe miraculously escapes, he is no longer someone the Jews want around. They want to remain positive that the stories they hear could not happen to them...in a way they want to remain blissfully ignorant of the truth. Moshe, much like the prophets in the Bible, have nothing but the truth to tell--even though it is not a pleasant truth. Therefore, the people choose not to listen and even to chastise him for what he says and what he represents (the dark side of humanity).
In the end, when the Germans show up and people start getting very worried that what Moshe has said is true, he simply disappears after telling them all once more, "You should have listened. Now it is too late for you, too."