And I know a lot of local Republicans who would absolutely write a letter like that. And they say much worse slurs in person.
Don't pretend that the Republican brand doesn't harbor racists especially when the facts are coming from a former Young Republican Leader such as Fukumoto.  And the hateful behavior in Virginia where the President defended Alt Right crazies who were chanting, "blood and soil", a known Nazi slogan. Or those same crazies who stood in front of a synagogue the night before with tiki torches screaming hateful anti semitist slurs. Your party voted for a president who said on tape he can grab a woman's privates while laughing.  Or tried to call out the parents of a Muslim soldier who sacrificed his life for this country. So I have no doubt that this letter is genuine.