I think it might be people's lack of thinking for oneself.
Bad things happen when people don’t think for themselves. When people outsource their thinking to others, genocide happens.
There is a school of thought that most people CAN'T think for themselves and that the masses should be governed be the elites. Not only do I think that is wrong but that line of thinking is also extremely dangerous. Because once you convince people they shouldn't think for themselves and they should think what you think … then that person is very susceptible to be easily influenced by others. Cults are generally not good … even cool Silicon Valley cults (like Google) can have their drawbacks.
When people think for themselves they need to take the first step and assume that they might be wrong and that some of their prejudices might be wrong. For thinking for oneself means evaluating the data available and coming to a conclusion. One could still reach a very bad conclusion … but one has a much better chance of helping themselves and helping society of they just think.