Last week, the Federal Bureau of Investigation did something rather peculiar—it publicly rescinded an internal memo on "radical-traditionalist Catholic ideology" the day after a whistleblower had published it. The shocking memo cited the Southern Poverty Law Center, an organization notorious for smearing mainstream conservative and Christian nonprofits as "hate groups" and placing them on a "hate map" among such groups the Ku Klux Klan. The document, titled "Interest of Racially or Ethnically Motivated Violent Extremists in Radical Traditionalist Catholic Ideology Almost Certainly Presents New Mitigation Opportunities," characterizes radical-traditional Catholics or "RTCs" by "the rejection of the Second Vatican Council (Vatican...