I think people are capable of recognizing that a writer can have both good and bad ideas. Charles Murray has made some interesting and original contributions, unlike his perspective on race and IQ which are neither.
While I don't disagree with this, it is also true that it's more than likely that Mr Murray used his credentials and standing to promote b.s racist theories. Given that it seems he did this on the one occasion it does raise serious questions as to whether any of his scholarship is valid.