I'll say I am not a open borders fan. It has nothing to do with racism. Most countries do have borders. Without borders there is nothing stopping a majority of people from any country coming into another country just because they are more prosperous and offer better opportunities. Over time there will be clogs in the arteries so to speak and opportunities will dwindle down to nothing. No country can support or survive from mass immigration into their system unabated, it just wouldn't work, it would take time to get to that point but in the end it would end up just as much a economic wreck as the countries they left.
You are right, racism is a learned behavior. I never brought my kids up distinguishing color. They never learned that skin color distinguishes us from one another, what distinguishes us is our character. There is the good, the bad and the ugly of the world and no one owns a franchise on any of that. My kids have had friends from all walks of life, that's much more an opportunity then my parents offered me. That's a lot to teach your kids coming from someone who practically grew up in fear of people of color. When I was a child I don't ever remember going to school or playing on a playground with children of color, now I watch my grand kids play with children from all backgrounds, when they run unto that playground the last thing they see is color, they are in joy to see other kids to play with.
I am not a fan of completely open borders either, my point is more about them just being conceptual lines in dirt subject to continual change.
It is and always will be the case. There is so much range in human nature but it is this continual negotiation that keeps us evolving. The children today will have vastly different experiences than we had as children.