Former New York Mayor Rudolph Giuliani wasn’t backing away from his questioning Vice President Joe Biden’s “mental capacity” for the highest office in the land, saying he is “one joke after another” during an appearance this morning on CBS’s Face the Nation with Bob Schieffer.

Giuliani went on to nail Biden in response to comments from fellow guest Senate Majority Whip Sen. Richard Durbin (D-Ill.) questioning his support for Sarah Palin four years ago, noting that Palin was a cut above the current BidVice President.

“After not knowing what state he was in or what century he was in within 24 hours and making what I would consider to be an absolutely disgusting appeal to racial sentiment, I said I wonder if he’s got the mental capacity to be the president of the United States,” Giuliani said. “This guy is one gaffe after another; he’s a joke on late-night television.

“I think they locked him in his room for the rest of the campaign.”

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The former New York City mayor went after Biden’s remarks ranging from his having told a guy in a wheelchair to stand up to his most recent episode telling a mostly black audience that Republicans want to put them “back into chains,” calling the latter an “appeal to racism.”

“Joe Biden’s gone too far,” Giuliani said.

If Biden were former Vice Presidents Dan Quayle or Dick Cheney, or even Palin, the media narrative and the rhetoric coming from Democrats would have been a lot different, according to Giuliani.

Durbin echoed the famous words used by 1988 Democratic Vice Presidential nominee Sen. Lloyd Bentsen against Quayle to rebut Giuliani, saying: “Joe Biden is my friend. Rudy Giuliani that isn’t fair. What you have said is going too far.”

“There isn’t a racist bone in Joe Biden’s body, and to suggest that is I think over the edge,” Durbin said.

The Senate majority whip refused to comment when Giuliani demanded an apology from Biden, saying he wasn’t “going to dignify those remarks.”