His point was that humanity doesn't like a period of extra long calm and happiness. And therefore they break down in a war-peace cycles periodically.
And watching US history that cycle is about 50 years. Thus 1970s Vietnam war and everything that came with it.
Before that the 1920s, great depression. And before it in 1870s. North and South -- US civil war on slavery.
This article is not a "found footage" kind of thing. I covered it in 2012 in a FB post when it was published. This article is getting renewed interest now.
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https://www.livescience.com/22109-cycles-violence-2020.html