Conservative writer David Horowitz accused the "anti-religious, anti-American left" of conducting an ongoing effort to erase God from American society dating back six decades.

During a recent C-Span event to talk about his new book "Dark Agenda: The War to Destroy Christian America," Horowitz argued that the progressive movement is trying to change the history on which this nation was founded.

"In the last 60 years, the anti-religious, anti- American left has conducted a relentless assault on believers and their beliefs, suppressing religious liberty, stripping the public square of religious expression and memory, and, in the process, removing the underpinnings of our democratic order," Horowitz said.

"What inspired me to write this book was the realization that the left's hatred for Christianity is also its hatred for America itself."

Horowitz then discussed the U.S. Capitol Visitor Center, which opened in 2008 and was built completely underground adjacent to the Capitol Building. The facility showcases the history of the United States and has several exhibits, a gift shop, and even a food court.

But what the center lacks, as Horowitz noted, are references to God — references he claimed were edited out of historical documents like the Constitution.

"All references to God and the religious faith of the founders had been systematically edited out of its photos and historical displays," he said. "The lengths to which the designers went to expunge God from the visitors center and from the founding is remarkably petty and extreme.

"Over the signers in the actual Constitution, it says, 'in the year of our Lord, 1787.' They photoshopped it so there's no 'in the year of our Lord.' Unbelievable, actually, what they did. The visitors center said that … our official motto is 'E Pluribus Unum.' No, it's 'In God We Trust.' And they took a replica of the speaker's roster, the speaker the House, which has the inscription, 'In God We Trust,' and they took it out."