I don't love this response, honestly, because it's very important to distinguish between theory and practice. People often celebrate America as they believe it should be. Responding by critiquing what America actually is is really talking at cross purposes.
I can see that, but I think when this is coming from a rich white person who doesn't really seem to do much work on the ground (wrt racism) the response is understandable.
Also, fun account: @YesYoureRacist - basically just names and shames racists who go out in public.