I thought I read one of the revelations of the most recent (2017?) de-classifications of some of the JFK assassination files was that “Landslide Lyndon” was a KKK member. I suppose this was pretty common for southern Democrats. (And all southerners were Democrats, basically)
In Basic Training as a rural midwesterner I was exposed to some interesting dichotomies. Chicago born Calypso Louis nutbars who wanted to fight, and southern good old boys who insisted the KKK was really sort of like the Elks Club or something.
A simple search finds https://thepoliticalinsider.com/lyndon-johnson-kkk/ states “Released JFK Documents Suggest Lyndon Johnson Was Former KKK Member”
And even msnbc states “Lyndon Johnson was a civil rights hero. But also a racist.” But that, “Johnson was a man of his time, and bore those flaws as surely as he sought to lead the country past them” - https://www.msnbc.com/msnbc/lyndon-johnson-civil-rights-racism-msna305591