There's a lot of history about, so can I forgiven for not knowing this until it turned up in a Twitter thread recently?:
Stetson Kennedy, a folklorist and social
crusader who infiltrated the Ku Klux Klan in the 1940s and wrote a lurid
exposé of its activities, “I Rode With the Ku Klux Klan,” died on Saturday in St. Augustine, Fla. He was 94.
The cause was complications of bleeding of the brain, said his wife, Sandra Parks.
Mr.
Kennedy developed his sense of racial injustice early. A native of
Jacksonville, Fla., he saw the hardships of black Floridians when he
knocked on doors collecting payments for his father’s furniture store.
His social concerns developed further when he began collecting folklore
data for the Federal Writers’ Project in Key West, Tampa and camps for
turpentine workers in north Florida, where conditions were close to
slavery.
After being rejected by the
Army because of a bad back, he threw himself into unmasking the Ku Klux
Klan as well as the Columbians, a Georgia neo-Nazi group. He was
inspired in part by a tale told by an interview subject whose friend had
been the victim of a racial murder in Key West.
As an agent for the Georgia Bureau of Investigation, Mr. Kennedy, by his
own account, infiltrated the Klavern in Stone Mountain and worked as a
Klavalier, or Klan strong-arm man. He leaked his findings to, among
others, the Washington Post columnist Drew Pearson, the Anti-Defamation
League and the producers of the radio show “Superman,” who used
information about the Klan’s rituals and code words in a multi-episode
story titled “Clan of the Fiery Cross.”
That's from his New York Times obituary, and it goes on to note some controversy over his claims, and this is explained in lengthy detail at Wikipedia.
The main reason I am inclined to post about it is because I didn't know the KKK was mocked in the Superman radio show. According to this site's account, the show really was influential in the decline of the outfit:
The Superman
writers created a thinly disguised version of the Ku Klux Klan for "The
Clan of the Fiery Cross". A newly revived Klan had emerged in the
aftermath of WWII
and was making plans to expand recruitment into the Industrial Belt and
the West. Folklorist Stetson Kennedy had infiltrated the Florida branch
of the revised Klan to learn their secrets and became understandably
frightened by what he had learned. Even more frightening, when Kennedy
presented his discoveries to local authorities, the police were either
frightened to move against the Klan or were already under Klan control.
However, Kennedy was able to share his information with the Superman writers.
"The Clan of the Fiery Cross" story
arc was developed and broadcast in June of 1946. The story begins with
Jimmy Olsen managing the Unity House baseball club and excited over
their prospects with new pitcher Tommy Lee whose family recently moved
to the neighborhood. Naturally, this upsets the team's former pitcher,
Chuck Riggs, who crowds the plate during batting practice and
accidentally gets beaned. Riggs' uncle Matt, the Grand Scorpion of the
Clan of the Fiery Cross, decides that Tommy Lee and his family are not
"real Americans" (it is not revealed until the third episode that Lee's
family are Chinese and his father was appointed to the city medical
department over one of Riggs' friends).
Through most of the sixteen episodes of the "Fiery Cross" story arc, the Clan and its Grand Scorpion manage to stay one step ahead of the Man of Steel until they try to execute Jimmy Olsen and Daily Planet editor Perry White. Superman steps in with seconds to spare, but the Grand Scorpion escapes to confer with the Clan's national leader, the Grand Imperial Mogul. The Mogul berates the Grand Scorpion for actually believing the Clan's racist propaganda, stating that it was simply a device to get new members and that the Clan's hierarchy was taking a cut on the sale of robes. The real KKK found nothing amusing about the story arc and tried to start a boycott against the sponsor, Kellogg's PEP Cereal. By this point, the Klan had been made to look foolish, the boycott went nowhere, and Mutual reported an increase in Superman's ratings.
Interestingly, the Fiery Cross story
arc kept the actual Ku Klux Klan thinly disguised, but the real damage
to the Klan came in the fourteenth episode when Matt Riggs visits the
national leader, The Grand Imperial Mogul of the Fiery Cross. The Mogul
cannot believe that Riggs believes the hatred hokum the group uses to
attract "the suckers". Had the Klan simply ignored Superman's accusations,
the revelations of their ceremonies and codes probably would have
dismissed or forgotten. Instead, the Klan began calling for a boycott
against the program's sponsor, Kellogg's PEP Cereal. To Kellogg's
credit, the folks in Battle Creek stood by the Man of Steel. The Klan's
reputation and power depended upon their mystique. With their ceremonies
and secrets revealed and made to look ridiculous, the Klan's mystique
and power evaporated. Recruitment dried up in the months after "The Clan
of the Fiery Cross". The Klan resurfaced briefly in the late 50's and
early 60's, but they were recognized as being little more than a white
supremacist terrorist group with little or no political power. The
most important lesson of The Clan of the Fiery Cross is that the power
of hate groups evaporates when the light is shone on them and their
tactics.
Yay for Superman, I guess...