DeChristopher spent 21 months in prison after he interrupted and undermined a federal oil and gas auction for lands adjoining national parks in Utah. He explained his reasons, saying, "It was kind of a prime example of the drill-now, think later mentality that's really driving the climate crisis."
He also said he had no strategy in mind when he arrived at the auction other than "making a speech or standing up and yelling. It was right after that guy threw a shoe at [George W.] Bush, so that was kind of in the back of my mind."
"Did you have a spare shoe with you?" Letterman asked.
DeChristopher was admitted to the auction as a bidder and began bidding to drive up the price. Then he began winning bids on various parcels - until he was hustled out of the room and was eventually charged, tried, convicted and sentenced to prison.
"Here's how dumb I am," Letterman said. "What you have have described ... sounds like a prank. How do you end up doing two years in a federal prison for what sounds to me like a prank?"
"Part of it is certainly that the people who lost money because that auction was disrupted are the people that control our government and pull the strings at a lot of our federal agencies, including our Department of Justice," DeChristopher said. "So they were certainly upset."
"But why couldn't they have said, 'Remember Bidder 70? Forget all that. We're starting over,'" Letterman said.
DeChristopher, who came across calm, cool and personable, said he believes "people were ready for something like this in the climate movement" and that it "really vaulted me into a new role for the movement where I was out there speaking about civil disobedience. I was traveling around the country as an activist at that point. And people were listening."
Letterman appeared most surprised when DeChristopher said his 21 months in federal prison left him "better off."
"I expected to go to prison," he said. "Prison turned out to be not nearly as bad as I expected."
"Now that can't possibly be true," Letterman said.
But DeChristopher insisted it is.
"One of the consequences of mass incarceration is that our prisons are filled with really normal people," he said. "Mass incarceration didn't happen because of some drastic shift in human nature, it happened because the private prison industry was able to change our laws that allow us to lock up a lot more normal people."
"Well, that's how we get our audience," Letterman said.
Letterman doesn't often take on environmental causes on the air, but he certainly seemed taken with DeChristopher and his story.
"At some point you can say to your family, to your friends and to yourself, 'I tried. I tried to do a little something. I tried to help,'" Letterman said.