Are We But Racists?

As an addendum to my previous post, consider the following. Scientists have confirmed with genetic testing that human beings crossed-bred with neanderthals.
In the 1990s, researchers began finding fragments of Neanderthal DNA in fossils. By 2010 they had reconstructed most of the Neanderthal genome. When they compared it with the genomes of five living humans, they found similarities to small portions of the DNA in the Europeans and Asians. 
The researchers concluded that Neanderthals and modern humans must have interbred. Modern humans evolved in Africa and then expanded out into Asia and Europe, where Neanderthals lived. In a 2012 study, the researchers estimated that this interbreeding took place between 37,000 and 85,000 years ago.
In a rare act of mercy, I won't name any names in this post. However, the argument has been advanced in certain sectors (over and over and over again) that human beings are incapable of getting along in large, diverse, cosmopolitan communities. It has been said that history proves that this can only end in violent conflict.

I have the links to where this theory has been advanced, but you guys know who you are, don't you.

Anyway, I just have to laugh. History shows that we hate diversity so much that we are willing to breed with members of a completely different species, so long as they look a little bit like us and we find them sufficiently attractive.

So was this isolated happenstance? Some ancient pervert decided to get it on with a neanderthal, staining mankind's tradition of ethnocentrism forever? Or, is human history actually a tale of remarkable outreach and the peaceful pursuit of positive relationships?

Remember, we're broadcasting radio waves to space aliens even as I type this, hoping that we get an answer. Well sorry, alien ladies, I'm off the market. But I hear all those guys who took the "Red Pill" are really good at courting your submission.