When the world’s largest conference on sustainability and green construction comes to Washington, D.C. on the cusp of a presidential race and titles its opening plenary “What Will It Take to Get Meaningful Action on Climate Change?” you might expect an “us vs. them” attitude and perhaps a little Republican-bashing. But although Greenbuild 2015’s kickoff event was politically minded, the tone was anything but rancorous.

James Cameron, photo courtesy Greenbuild International Conference and Expo

U.S. Department of Housing and Urban Development secretary Julián Castro, his tie a bipartisan shade of purple, opened with a talk on how sustainability benefits everyone, from governments to businesses to the man on the street. “Green building is not a slogan,” he said, “but a solution”: for healthier homes and environments, for greater resilience to increasingly severe weather, and for economic growth. Apart from briefly mentioning the Obama administration’s green bona fides, the closest Castro came to campaign rhetoric was his observation that by creating more sustainable buildings and communities, “we are ultimately building a stronger America.”

Rick Fedrizzi, U.S Green Building Council founder and CEO, looked to raise the excitement level when he walked onstage to discuss the state of the USGBC. Instead of shaking fists at politicians and corporate leaders who view climate change as a myth, Fedrizzi exhorted Greenbuild attendees to extend their arms in a business handshake. “There is a Republican, pro-business argument for sustainability,” he said. “To catapult ourselves to the next level, we need to use the power of the profit motive.”

In the event’s final segment, Fedrizzi’s tent-revival energy gave way to a relaxed conversation between MSNBC’s Morning Joe co-host Mika Brzezinski and James Cameron, the award-winning filmmaker now known as much for his environmental passions as for his blockbuster movies. Cameron surprised Brzezinski, and the audience, when — after saying, to widespread cheers and applause, his “dream government” would price carbon — he noted that animal agriculture is the second-largest contributor to greenhouse gasses. Using his own conversion to a fully plant-based diet as a starting point, Cameron waxed passionate on how vitally important it is to shift away from a meat-and-dairy-heavy diet, and the environmental impact such a change would have. “Food is not on the table in the climate discussion the way it should be,” said Cameron — a result of the “nature deficit disorder” that plagues our increasingly urban society. “Ultimately,” said Cameron, “it’s all about conscience. You can’t protect what you don’t respect.”