It seems unlikely to me that the KKK would have offered her a dozen invitations to tell their organization how to keep their own numbers down. In any case, the content of her speeches don't matter. If she had been a Republican, the mere fact that she was seen in the company of the Klan would have destroyed her credibility forever and any recipient of a "Maggie" would be deemed a certified racist.
Think Sanger was a Fabian Socialist at that time.