@snood,
Absolutely not, they will not have similar attitudes. I did not say that racism in in us at birth. If my statements inferred that, they were poorly written.
The instinct to protect the group is part of who we are. That protection may take the form of deciding that an 'outsider' is a danger to the group.
What I meant to say was that the motivation to protect a group we are a part of is very strong, and is part of our intrinsic behavior. Yes, this group educates us and forms our opinions, good or bad.
In your example, if these two children met in school, they may in fact fight with each other, seeing the other as a threat to the famly they are in.
I would agree that we are taught to be racist. Our motivation to accept that teaching, rather than question it, comes from our need to belong.