(CNN) Rudy Giuliani, the former mayor of New York City and the current public face of President Donald Trump's legal team, sat down for an interview with CNN's Chris Cuomo on Tuesday night . It was contentious -- if generally friendly -- and ended with this exchange:

CUOMO: I think it's a little early on that. And if fact [checking] is anything, we've never had anybody with the level of mendacity that he has. Not even close.

GIULIANI: It's in the eye of the beholder.

CUOMO: No, facts are not in the eye of the beholder.

GIULIANI: Yes it is -- yes they are. Nowadays they are.

The specific context of the exchange was Giuliani making the case that Trump has more accomplishments in 18 months than his predecessors had in eight years. (Giuliani also said this of Trump just before the above exchange: "Maybe nobody has been as honest as him." Riiiiiight.) But the context doesn't really matter as much as the content.

The argument Giuliani is making is one we've heard before from this White House: You're entitled to your own facts.

two days after Trump was sworn in as the 45th president in January 2017, senior counselor Kellyanne Conway was challenged by NBC's Chuck Todd over claims made by White House press secretary Sean Spicer that the Trump inauguration featured the largest audience in history. "You're saying it's a falsehood," Justdays after Trump was sworn in as the 45th president in January 2017, senior counselor Kellyanne Conway was challenged by NBC's Chuck Todd over claims made by White House press secretary Sean Spicer that the Trump inauguration featured the largest audience in history. "You're saying it's a falsehood," Conway responded . "And they're giving -- Sean Spicer, our press secretary -- gave alternative facts."

16 things that were misleading or flat wrong, again according to the Fact Checker. Conway sought to distance herself from the "alternative facts" construct in the days that followed, but the idea stuck because, over and over again, President Trump said things that simply weren't and aren't true. In his first 558 days in office, Trump said 4,229 things that were either misleading or outright false, according to statistics maintained by the indefatigable Washington Post Fact Checker . Trump is averaging more than 7.5 false claims every single day of his presidency. Every single day. And he's picking up steam; in June and July he said, on average,things that were misleading or flat wrong, again according to the Fact Checker.

There is absolutely no precedent for this sort of mendacity -- in any politician, much less in a president of the United States. And it's not just the raw number of things that Trump says that are partially or totally wrong, it's how he glorifies what he is doing -- and uses his fact-free approach as a cudgel with which to beat up the media.

"Stick with us," Trump told a group of veterans in late July . "Don't believe the crap you see from these people, the fake news. ... What you're seeing and what you're reading is not what's happening."

The cynicism in that statement is towering. Trump has no real answer for the amount of mistruths and outright lies he tells. But he knows that his base hates the media and that, by making all of this about how the press covers facts as opposed to the facts themselves, he can muddy the water more than enough to turn his lack of fact-based statements into an applause line at a campaign rally.

That's the thing here. Trump, Giuliani, Conway -- they know what they are doing. And at least the latter two know the danger of it. If we can't agree on a set of facts, we can't talk. We can't debate. And we sure as hell can't break the death grip that reflexive partisanship has on the country at the moment.

That reality is more important than any political calculation. Sure, running down the media -- and with it the idea of objective truth -- is a nice juicy rare steak to toss to your political base. But it comes at a significant cost. If you keep saying stuff like "alternative facts" or that facts are "in the eye of the beholder," you erode out the very idea of truth. And that's not something -- once damaged -- can or will recover quickly, if it recovers at all.

In short: We all need to be the Cuomo of this exchange. No matter where your politics lie, you need to affirmatively stand for the idea that facts are facts.