The reason for this behavior is a nurture thing. Books with white hero's, white hero's on television, in adverts,...
That doesn't make any sense... Prior to an,ything, you have to acknowledge the existence of "white people", I personally am not white but insular celt, and see no point in putting myself in the same box as Germanic, Latin, Levantine... people. Secondly, and admitting there are "white people", which seems more of an american term, relative to american society only, then you'd have to explain how and why it give such behaviour and why a "black" or a "yellow" or a "purple" hero isn't a problem, especially in a I don't know what colour dominated land.
Same, what would happen if showed only animals to children? Like only Rabbit heroes. Would they suddenly become specist? Why? How?
As for the Doll experiment, this could just reflect the surroundering of the kids, just like you probably mostly hang out with people similar to you for a reason that could probably be found for a part in evolutionnary biology itself rather than solely blaming the society.
Concerning the rest of your message, I'll repeat myself: School already showed its limits. Back then, France used to taught children to be very patriotic and/or nationalist, and to be recentful toward Germany. However things have widely changed over the time to the point that many French people are against nationalism and like German people. I wonder how could it be possible if education didn't fail somewhere at creating perfectly - this word is important - endoctrinated citizens.
Back to the topic itself. I'd feel better knowing some skillfull citizens could react at the moment iif something wrong happened rather than relying on the police knowing that I'd have to wait for them.