I feel racism is a consequence of slavery. Because people of black skin were forced into slavery, and their lands exploited, this led to a stigma being placed on people of that skin color.
That's where racism gets its power from.
Also because those lands were exploited, it is kind of much harder for those lands to catch up with those in the west. And because of thus 'backwardness' it seems to give fuel to racism.

I feel this is the connection.