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Former Sen. Joe Lieberman cautioned Democrats Friday against harshly questioning presumptive Supreme Court nominee Amy Coney Barrett on her Roman Catholic faith, warning such a line of inquiry will "hurt her opponents."

"You can disagree with somebody based on whether they're pro-life or pro-choice," Lieberman, the 2000 Democratic vice presidential nominee, told "Your World."

"But when you start to say that you're against them because their religion, in this case, their Roman Catholicism determines their point of view," he added, "you're doing something really abhorrent that I think is bigoted, is un-American, and incidentally, is unconstitutional."

Lieberman emphasized that "Article VI of the Constitution says that you can't apply a religious test for any office of public trust in America. That's how wise and fair the people who wrote the Constitution were."

FLASHBACK: AMY CONEY BARRETT PRESSED BY DEMS IN 2017 HEARING OVER CATHOLIC FAITH: 'DOGMA LIVES LOUDLY WITHIN YOU'

Earlier in the segment, Lieberman -- a self-described "religiously observant Jew" recalled his early runs for public office in Connecticut, a state with a large Roman Catholic population.

"I found that the fact that I was religious and observant was actually a tie, a bond [with] people of other religions who were similarly observant."

Later in the interview host Neil Cavuto referenced Sen. Dianne Feinstein, D-Calif., who told Barrett during her 2017 confirmation hearing for a seat on the appellate court, told Barrett that Catholic "dogma" seemed to live "loudly" within her.

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"I thought Sen. Feinstein's question in that case," Lieberman said, "was really improper, and was biased really. Everybody brings to the Senate, to the Congress, to [the] Supreme Court experiences and beliefs that they have.

"There's no reason why a religiously observant person should be accused more of dogma than somebody who is particularly ideological in a secular way."