“But a given racist can otherwise hold conservative political opinions with which I agree.”
Yes, and remember, at that time Duke and his cronies were trying to infiltrate the Louisiana Republican party, so they were adopting stances (at least publicly) that were very close to standard Republican stances, and shying away from their crazier rhetoric.
I have heard Duke speak on several occasions, perhaps C-Span, and you are right. Even a libtard reading the transcript, without knowing who was speaking would have found nothing more objectionable than the usual D-R policy differences. He disguised his racism well.