What you're talking about are things that happened in larger cities, but that's not the whole world and that doesn't match the history of much of the midwest.
The parent was right, if there is discrimination it's about culture not color. There were a few adopted children with heritage from different parts of the world and as far as I could ever tell, they were treated the same as anyone.
The discrimination you did see to any degree was on a protestant/catholic split and whether you lived in a relatively richer part of town.
I just didn't see racial hatred growing up. Actual racism was a foreign concept until I left. Something you saw on TV, not in real life. I'm aware that it isn't necessarily something I would have always seen... but I have seen racism since I left in a way that I definitely did not before.