Racism isn't about noticing the glorious diversity of skin tones, facial features, and body types that constitutes humanity. Neither is it negated when you welcome "differentness" into your community.
Racism is about power. Those who have it rarely share it gladly.
As the "others" grow in number and begin to clamor for a role in governing the community, the powerful will look for ways to keep them in their place.
Racism is division. They divide us to defeat us, make us fear and fight each other, hoping we we'll forget the ugly truth of how unevenly the nation's wealth (and therefore power) is distributed.