As long as there are fearful, cowardly, splintered people who want to feel superior to others by any means, and who project their weaknesses, failures and fears onto others, we will see the book re-opened and re-played.
We are all not better, nor worse than others, just different, and that's how the universe rocks and rolls.
The usual appeal is to racism "but they're different", immigrants, people of different belief systems, people from other countries, and people fall for it, because they want to feel superior and privileged without having to earn that privilege.
We are all different.
We all have different beliefs, viewpoints and experiences.
We all were born somewhere, not somewhere else, and were brought up in that regional culture.
It's incumbent on this warring human race to recognize our 99.99999% commonality and get along, and make ourselves better by making life better for others. It's the old "rising tide", and "golden rule" maxims that are ignored, because the part of us that dodged saber tooth tigers still resides in us, mainly to dodge autos these days, but is only part of a spectrum of feelings we can attain.
Hate and fear are their own rewards, and crappy ones at that.
But easily stirred by real discontent, or manufactured discontent consisting of repeated exaggerations and lies.
Get real. This is all bullshit, to our disadvantage and someone else's (i.e. cult leader's) advantage.
To wit:

The Science Fiction writers were right. We snap out of this mutual hatred, envy and war or the planet is doomed (more than it is now).
How? Well, weren't you and I put on this planet to find out and to make happen?
Even if we need a little outside help?

To Serve Man