WATCH: Furious Rob Reiner opens up a can of whoop-ass on Rick Santorum for repeating Trump's lies

Former Senator Rick Santorum ran into a buzzsaw during the panel discussion on HBO's Real Time Friday night, with host Bill Maher and guest Rob Reiner taking shots at Santorum for continuing to back GOP presidential nominee Donald Trump.

It was a contentious segment with everyone on the panel -- including conservative commentator Tara Setmayer -- hammering on a clearly pained Santorum who maintained his support for Trump while at the same time admitting that the new face of the Republican Party is a flawed candidate.

While Maher got off some harsh comments on Trump and his followers -- calling his voting base “fact-free racist rednecks” -- it was director Reiner who brought down the house with a furious attack on Santorum for repeating one of Trump's more egregious lies.

When Santorum defended Trump, comparing his constant lying to Hillary Clinton, Reiner blew up.

"No no no no," Reiner exclaimed. "You just say a line like that, you just say it, and it's not true!"

After Santorum claimed the FBI said Clinton lied, Reiner hit back, "Let's talk about the FBI!"

"There was one email, "Reiner said with his voice rising. "One email that was not listed as classified -- with a little tiny 'c" -- and James Comey said anybody could have missed that! Enough of that! Enough of that!"

Following furious cross talk, Santorum could be heard muttering, "They're both flawed candidates."

Watch the video below, uploaded to YouTube by Mediaite: