In his testy exchange with two Tea Party members in Iowa last week, President Obama denied that Vice President Joe Biden used the word "terrorists" to describe conservative groups. But now Politico, which broke the initial story, has detailed its reporting in ways that convincingly paint the veep as guilty of the charge.

For one thing, Politico reports that "the vice president's office has not asked for a correction or retraction," which would be standard in such an important matter. It also says it had five sources inside the Democratic caucus meeting who heard Biden make the remark.

According to Politico's recounting, a reporter contacted Biden's office after talking to the sources and came away "confident" the story was accurate. Hours later, after the story appeared online, Biden's office issued a non-denial denial, saying "The word [terrorist] was used by several members of Congress. The vice president does not believe it's an appropriate term in political discourse."

This is not a typical Biden gaffe that can be laughed off. The vice president of the United States has outrageously compared American citizens to violent enemies of our nation for daring to exercise their democratic rights to dissent.

An honorable man would admit it and apologize. Until he does, the words directed at Sen. Joseph McCarthy in 1954 apply to Joe Biden today: "Have you no sense of decency, sir?"

Michael Goodwin is a New York Post columnist and Fox News contributor. To continue reading his column on other topics, including on New York's Governor Andrew Cuomo, click here.