A fun narrative, but likely inaccurate.

The reason the genocides in Africa occurred is the same reason all violent racism starts (regular ass racism starts with income disparity and unfamiliarity, but thinking that a group is inferior is different than wanting to murder them.) It's actually incredibly understandable; it'd have to be, because it can, of course, happen everywhere.

You start with a group of people who are having a real shitty time. Usually this means poverty, for whatever reason. Not a lot of work, not a lot of money, people are hungry, there's a problem. Well, the government, entertainers, pundits, revolutionaries, etc. can't actually solve these problems. This is because solving poverty is actually incredibly difficult and can't be done quickly. But, they need to keep their viewers, or their votes, or their lives, and if you can't placate the angry population, you need to at the very least turn the anger away from yourself and towards your enemies. Revolutionaries just need to promise that they'll be better; the anger is already pointed in the right direction.

Being able to blame a group of people is incredibly easy, because it simplifies something complex. It makes it understandable, and you can incorporate it in to your mental schema without a whole lot of effort. Are you hungry, are you out of work? Well, it's not you, it's not the economy; the jews stole your jobs. Or black people. Or other white people who aren't your specific type of white person. Or they're just a general blight on the country.

Violent racism in America, the one that wasn't just outright slavery, came about not because of rich white southerners but because of poor white farmers. Why? Well, they went from having no competition for work to having almost 30% of the population as competition for work. Plus they had just lost a war, and weren't really getting any benefits from it. And they had lost it hard by the end, when they came so close to winning. All to free people who they hadn't even thought of as humans. The first person who stood up at a public meeting and said "fuck all black people" turned all of those negative emotions in to a very solid, very coherent hatred.

Why did violent racism diminish over the course of the 20th century? Well, that's also really simple. After World War 2, we had a lot of money. Money buys food, and it buys things that are fun. It relieves stress, mainly the stress of not having money. We just won the war. Sure the racist attitudes were still there, because they had at that point been ingrained in the culture for so long that they still persist, but it became a time when people would even bother to look at civil rights. It just took a couple of years of pushing. Realistically, if we had been poor as we had been during the Depression when the Civil Rights movement took to the streets, it would've gotten no where.

First you eat, then you care about your fellow man.

This is true in the middle east. It's actually a really simple formula. The region is by and large very poor. Wealth distribution is bad; oil, after all, only benefits the people rich enough to extract it. It's also war torn, and it's been war torn since the 1900s, well before Israel was even a twinkle in the eye. It went from being the Ottoman Empire, a powerful, if bloated, political and military force that commanded some serious respect for centuries, even when it was technologically behind the rest of Europe. Prestige goes a long way to relieving national stress, after all.

Blaming the Jews, blaming the other sects of Islam, it's all a very simple and very old method of getting people to look away from the fact that their wallets are empty. Same with Rwanda. Same with China. The best way to alleviate it? Build up industry, get people jobs. Everything else is a bandage.