This is fresh air, I'm Terry Gross.

Today's political extremism has roots in the past.

The organization that did more than any other conservative group

to propel today's extremist takeover of the American right

is the John Birch Society.

That's according to the new book Burgers,

how the John Birch Society radicalized the American right.

My guest is the author, historian Matthew Dalek.

The society was known for its opposition

to the civil rights movement, its anti-semitism,

its willingness to harass and intimidate its political enemies,

and for spreading conspiracy theories.

Communist plots were alleged to be behind many things

the Burgers opposed, from the UN,

to teaching sex education in schools,

and putting fluoride in the water supply.

The group was founded in secret in 1958

by the wealthy, retired candy manufacturer Robert Welch,

whose candy is included sugar babies, junior mints,

and pom-poms.

The people Welch first invited to join the society

were also wealthy white businessmen,

...