Why did african american and other minority men find postwar discrimination especially upsetting?

In the postwar period, the situation was not changed dramatically when it came to racial discrimination int he United States. There were still many people that didn't wanted to have anything with the people of other racial groups, and did not saw them as equal to them. This was very upsetting for the people of other racial groups, such as the African Americans, Native Americans, the people of Asian ancestry, especially because they risked their lives for the country and for the people living in it during the war. They could not understand who is it possible that they put their lives on the front in order to protect the others, just to be discriminated again when they came back home by those same people that they were fighting for.