The “American Dream” remains real in his dementia

He came to America with pennies in his pocket, brought his children with a dream, called the ‘American Dream.’ The children were teased and called ‘japs’ & ‘chinks’ but still believed in the same American Dream. We studied & worked hard, and between us & his grandchildren employed thousands of Americans and paid our fair of taxes without complaints.
Now, the long arm of age has cursed him with dementia. When I say America has changed he gets angry and rebukes my attitude and tells me to be thankful.
How do I tell him that there is an ugliness that he doesn’t see? Some people would rather that we never belong here no matter how we contribute to society.
Ironically, I’m glad that dementia will at least keep his American Dream real for him forever?