"Sacha Baron Cohen was trying to get Governor Palin to say something homophobic and hateful," a source tells PEOPLE of the interview

Sarah Palin recently revealed she was “duped” by actor Sacha Baron Cohen, who disguised himself as a disabled U.S. veteran to interview her for his upcoming Showtime series, Who Is America?.

And a source tells PEOPLE that the former Alaska governor, 54, walked out of the prank interview after the disguised Cohen asked her a “horrible” question about Chelsea Clinton.

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The interview, which taped in November 2017, was booked through a speaker’s bureau that was working with the former Republican vice-presidential candidate at the time. “The request was very sophisticated and looked legit,” the source says.

“All of it was obnoxious, but I think the last straw was when the interviewer asked about what he claimed was a government-funded sex-change operation for Chelsea Clinton,” the source says. “Cohen was trying to get Governor Palin to say something homophobic and hateful. She takes it personally when anyone goes after the children and families of politicians. She just thought, ‘What a horrible thing.’ She was particularly incensed about that.”

Image zoom Sarah Palin; Sacha Baron Cohen Larry Busacca/Getty; Jason Merritt/Getty

Palin previously shared that she and her daughter were asked to travel across the country for the interview, where she claimed Cohen had “heavily disguised himself as a disabled US Veteran, fake wheelchair and all.”

The source explains Palin and 17-year-old daughter Piper arrived at the specified Washington D.C. location, where Piper was taken to a separate trailer while her mom was interviewed. “For an hour and a half, they wouldn’t let her go,” the source says.

All these months since, Palin had no idea who was behind the prank.

“We had our suspicions, but they did a very good job of setting it all up,” the source shares.

A representative for Cohen declined to comment.

Image zoom Patrick Semansky/AP

Chelsea Clinton with father, former president Bill and mother, former Democratic presidential candidate Hillary

Palin’s claim about being unwittingly interviewed by Cohen comes five days ahead of the July 15 premiere date for his Showtime show, Who Is America?

On Monday, The Hill reported that Drudge Report chief Matt Drudge tweeted a warning about Cohen’s antics on Monday, a day after the comedian released a trailer that appeared to show former Vice President Dick Cheney signing a “waterboard kit.”