This is an interesting article...if I'm reading the tables right, it appears that almost 30% of Southern whites were considered to be sympathetic/supportive to extreme right wing groups. All are assumed to be white, but racism isn't explicitly discussed as one of their beliefs, only anti-communist and anti-change sentiments...
Did/does "anti-communist" serve as a euphemism for race issues?
Part of a larger article posted on an ultra-rightwing website... note the links back to Stormfront.org - one of the oldest continuing online discussion forums for neo-Confederates, neo-fascists, Christian identity hate groups and other ultra-conservatives. This page shows a picture of King in the company of "subversives" such as this one that the New Orleans police took when they raided SCEF offices - the notations on this MLKjr website include citations from the Congressional Record where the descriptions of the Bradens and SCEF as "communist" and advocating class/race warfare can be found