Climate activist Tim DeChristopher has been out of federal prison for more than six months now, following his incarceration for disrupting a public mineral rights auction in 2008. (DeChrisopher outbid actual oil and gas companies for leases on land surrounding Canyonlands National Park.) And while he may have been banned from dangerous acts of “social justice” after his release, he’s not banned from talking about them!

Last night DeChristopher was on the Late Show with David Letterman to talk about Bidder 70, the documentary that chronicles his civil disobedience, walking a friendly but confused Letterman through the day in question.

Highlights from their conversation: Letterman, perplexed as to why “a prank” would land a guy in prison for two years; the, um, upside? to mass incarceration (“our prisons are full of really normal people”); and what DeChristopher had planned to do that day at the auction, before someone handed him a bidder number (hint: remember the dude who threw his shoes at President Bush?).

[youtube=http://www.youtube.com/watch?v=pnRwqS25b6o]

Ultimately DeChristopher is a more optimistic man than Letterman. When the host asks him if it’s too late to steer us away from our impending eco-doom, DeChristopher has a little smirk. “I think it’s important to stop and think about what it means to be too late.”