As ugly and unfortunate as racism is, I don't think it's the main source of most serious problems. Certainly there are exceptions to this: slavery, white settlers v. Indians, the Holocaust, etc. But most problems are based on economic or security issues, and these are not race related in and of themselves. That is, you could take race completely out of the equation and these would still be issues that cause social problems.
Another way to look at this is to ask: if everyone were the same color, race, creed, and religion, would problems disappear? Of course not.