The racist "Ron Paul" newsletters are in the news again (just heard about it on NPR). If you know the story, basically Ron Paul and his supports claim that the racist comments were written by a staff member and slipped by Paul's lax editorial oversight; Paul disagrees with all of it, and there's nothing more to say. Unfortunately for Paul, there is more to say, and I doubt that he will say it because -- like most Republicans -- he doesn't understand the totalitarian danger that lurks in racism.
Most Republicans recognize that "racism is wrong", but it is the wrong sort of "wrong". They think of it as an intellectual error. Or a type of meanness. Either way, they think of it as a failure of the individual who is racist. They ignore any social aspects of racism more profound than self-segregation. They ignore that racism is fundamentally a political ideology, justifying the oppression of some people by others. They ignore that its continued prevalence is a social failure, not just a personal failure.
Most Republicans have internalized the conclusion that racism is "very wrong", but they way they apply this conclusion illustrates that they still don't get it. They still focus on the individual expressions of racism, while ignoring the social structure behind it. If one black racist acts threatening towards a white guy, they throw a fit and then get all self-righteous when the traditional anti-racist coalitions don't see it as anything more important than regular street crime. Republicans do this because they don't see the political nature of racism, and they can't distinguish between racism that is politically impotent (i.e. black racism) and racism that could lead to tyranny (i.e. white racism).
This is the stuff that Ron Paul doesn't get about racism, and why he too often tolerates the company of racists (e.g. the people who wrote his newsletters and his 2008 anti-Latino advertisements) -- he doesn't get how these individual acts fit into a larger system of oppression.
For more thoughts on related issues, see Gary Chartier's summary of the relationship between "left-wing market anarchism and Ron Paul"