There is obviously a huge cultural difference in the Sudan and California. One scene that particularly showed this to me was the scene on page 333, when some men from the SPLA are giving the boys a demonstration. They have hostages that they claim are rapists, thieves, and murderers, and they are shouting to the boys that they will not tolerate it. The men protest and say that they are members at the SPLA and did nothing, but the soldiers have made the boys so angry at these men with their accusations that the boys cheer when the men are shot.
Though Achak has never seen these men before, the shouts and excitement manipulate him. "We yelled no. I felt that the men should surely be punished for such betrayals. I hated the men." (334)
This was a cultural issue to me because though this seems wild and savage, it is also something I can visualize happening in a society that claims to be as civilized as we do. Obviously there are not demonstrations like this is Marin, because we claim to be "above" this kind of brutality and use a "fair, honest system."
However, before the holocaust, when Hitler was doing anti-Semitic demonstrations, he wasn't talking to a crowd of Nazis, he was talking to a crowd of civilized citizens. It is probable that before this, if you had asked one of those citizens if they ever expected to be part of the ostracism of jewish people, they would say no, claiming to be above it, as we do now.
So, in summation, I think this is a cultural thing in that humans are swept away by mass hysteria, and though the cultures are presently very different, it is in our nature to swallow the emotions being fed to us, rather than go against the crowd.