Political tribalism and group identification is easiest at the racial level. After more subtle differences intra-racially that caused political divides and conflicts have been made superfluous because of various political changes race identity becomes the largest remaining differentiator especially consistent with cultural differences. Group racial identity should not be taken out of context and assumed to be solely an evolutionary, innate trait inherent in all of any race conditioning social and political behavior. Racism is tied to definite economic factors and political economy as well as culture.
I wouldn’t at all agree that human behavior is inherently preconditioned. That seems silly to me. A huge amount of behavior is learned, and the learning is a consequence of circumstantial historical factors such as exists in culture, geography and political economy. People can change their behavior and attitudes toward race fairly easily as circumstances change- for instance as may occur in military socialization (we are all green) and in economic mutual advantage. Lizards of a given color have been studied and observed to have a cyclical battle with lizards of other colors, and programmers can write code to make programs biased toward other programs, yet humans have free will and are quite able to change their attitudes and ideas especially when it is to their economic advantage. B.F. Skinner observed certain characteristics of native human behavior that are organic, yet there is a large element of reason too, and a human capacity to organize based on rational expectations and goals that bring advantage to humans transcending of skin color variations and constants.