People find differences. Back then the places that didn't have a ready supply of colored folks (might as well use the adjective of the day) were treating the Irish and Italians and eastern Europeans like crap in their place.

1945 is kind of different because by then it was pretty clear we were all in it together but in 1940 or so there was still plenty of "white on white" bigotry targeted floating around. 20+yr later it was considered novel that JFK was Catholic.