Dan Barker tuned his radio to 92.1 FM (“the Mic”) in Madison, Wis., on Nov. 12 — just as he’s done almost every Saturday for a decade.

Usually, he hears his own voice waxing philosophically about issues important to atheists and other “cultural outsiders.”

But on that day, he heard something else: Elvis Presley crooning “Winter Wonderland.”

There was also “Carol of the Bells.”

And “Baby, It’s Cold Outside.”

That’s as far as Barker got before he cut off the radio, disgusted by the thought of Christmas music a month and a half before the actual holiday.

Days after Donald Trump was elected president and Republicans strengthened their grip on Washington, the people who put on the progressive program “Freethought Radio & Podcast” learned that it was off the air in Madison, where the show is based.

Taking its place: Christmas music.

All day, every day.

“After we produced the show last week but before it was aired, we found out, rather rudely, that the flagship broadcast had been preempted,” Annie Laurie Gaylor, one of the co-hosts, said during the next week’s edition of “Freethought.” “We had been replaced without notice with 24-hour, wall-to-wall Christmas music playing.”

Gaylor and Barker, who head the Madison-based Freedom From Religion Foundation and produce “Freethought” from their home, didn’t think the move was an insidious bid to squelch a counterculture voice. The foundation’s deal with iHeartRadio, which owns the station, allows for either party to cancel the month-to-month contract in Madison, Gaylor told The Washington Post.

The syndicated show is broadcast on a dozen stations and is also available as a podcast, but Madison’s WXXM (92.1 FM) was the flagship.

WXXM is now calling itself “Madison’s home for the holidays” and offering a mix of secular and spiritual Christmas songs.

Barker suspects iHeartMedia, the Texas conglomerate formerly known as Clear Channel, could make much more money airing ads after playing the Jackson 5’s “Santa Claus Is Comin’ to Town.”

Angel Aristone of iHeartMedia told The Post that the switch that flushed “Freethought” from the Madison station was part of a nationwide format switch.

“The station actually changed formats completely to all holiday music,” Aristone said. “We constantly review our programming and listenership throughout all our markets. Occasionally this means that we need to make some changes and offer other programming that we believe will resonate well with the audience — holiday music stations during this time of year are highly popular.”

Gaylor and Barker are trying to get onto another station in Madison. Listeners can still hear the show in other markets, including Milwaukee, or via podcast.

But the podcast is typically heard by people who already agree with the hosts’ point of view. Over-the-air broadcasting is a way to reach everyone, including the 23 percent of the population that the Pew Research Center says is not affiliated with a religion. Barker, for instance, recalled a truck driver who phoned in one day, saying he had happened across the broadcast while driving through Madison.

The show’s hosts also worry about anything that quiets the voices of atheists and agnostics after the nation elected a president who has been embraced by the religious right.

People with that viewpoint, Gaylor said, have a monopoly on talk radio. “You can turn on the radio 24/7 and get preached at,” she said. “And we feel that has to be countered. We think it’s terribly important to have a voice of reason.”

Gaylor added: “My reaction to all this is ‘Bah, humbug.’ ”

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