The truth is that American history (XIX century especially, but also before that) is horribly, appalingly racist. I cannot reconcile that fact with what you said about people in the past believing that everyone, regardless of race etc., can be made into an American.
One can act in way that we consider racist while holding idealistic beliefs. I fail to see why this subtlety of human behavior needs to be justified over and over again.
This is an extremely and purposefully disingenuous view of what I said.