For certain it is not simple enough that it is pure instinct. On that I will agree.
On the other hand racism is not so complex that a man or woman is not responsible for his or her own actions involving his or her racist views. One chooses to be a racist. Just as one chooses to accept the inherent differences of others.
In South Africa a white man or woman chose to support the system that survived on the back of exploiting the Black African population through Apartheid or they did not. There were examples of both and also of people in between.
There were anti-semitic people in Europe who participated fully with the Holocaust, and some who did not wish to carry it to such extremes. There were Roma who participated in the most violent reprisals against the Jews only to be the next group to face the wrath of the angry European whites as it said in the article I recently posted.
Racism is a very simple because it fills a base human desire. It places a group above another. Nationalism does the very same thing. Both fill a very simple need amongst many people. "You may be one of the dregs, you may be a nobody, but at least you're white. You can always look down on the other races."
Or:
"You may be a dreg, you may be a nobody, you may be a simple guy, but at least you're an American and you can always look down on people from other countries."
You can put any nation in there and it still works as long as you give them enough mythology and symbolism to fill their fantasies and make them feel that they are a part of something better than themselves. Racism and Nationalism are very basic and very similar.
Buy a bunch of lapel pins from China and whoever doesn't wear them isn't part of the group. In other words, if you wear one you're better than those who don't. It is easy - that's why I don't consider it complex. The psychology is simple. The methods are simple and almost universal. For the elite it is always a good method of distraction. When the shit is really hitting the fan - start blaming the people who are different for everything. There's nothing new or complicated about it. The language hasn't even changed very much.