I also don't remember ever saying being racist made someone wrong. I said being racist made it difficult to have one's opinion on anything (especially race-related issues) be taken seriously when said racist has already demonstrated an eager willingness to make judgement on someone based on their race. Put another way, being a racist pretty much makes you an idiot, so how much faith can I put in your intelligent, well-thought-out point of view?
An obese guy might have a PHD in nutritionology, but damned if I'm gonna let him give me advice on living a healthy lifestyle.