Why are the prisoners so angry with the newly arrived Jews in Night?
The prisoners are angry that the new Jews have arrived because they think they should have known better and had a way of getting away since it is 1944.
When they first arrive, they are given advice. Elizer is told to say he is 18 and not 14, and his father is supposed to say he is 40 and not 50. This advice will keep them alive.
Some of the other prisoners there are not as helpful. They are angry that prisoners are still being brought there. They think they should have known better. Even when the new prisoners say they had no choice, the old-timers get angry.
"Shut up, you moron, or I'll tear you to pieces! You should have hanged yourselves rather than come here. Didn't you know what was in store for you here in Auschwitz? You didn't know? In 1944?" (ch 3)
This anger is a result of the fact that they despise that prisoners are still being brought to Auschwitz. It means that people still do not know what is happening to them. The outside world does not know what is hapenning. Every new transport of prisoners makes them lose a little bit more hope.