Business leaders and environmental activists never kept close quarters, until Walmart invited Al Gore to Bentonville to airThe Inconvenient Truth .

Of course, that was long after the retailer first became the subject of criticism from conservation, labor and other groups. Speakingat the Fortune Brainstorm Green conference in April, former CEO Lee Scott admitted that Walmart’s eco focus only got its start when the company decided that, rather than play defense, it would hear out its critics. The unusual alliance was also an uneasy one early on: when Walmart first invited the green-minded groups to Bentonville, the activists made it a requirement that the retailer wouldn’t disclose the meeting even took place. 

Half a decade later, much has changed, with Scott relaying how many of those critics are now championing Walmart’s efforts. “We may have disagreed on certain points, but they really wanted us to take a leadership role,” he said. “And when we did that, they were just as willing to give us credit as to criticize us.”

It’s a point brand owners might be waking up to as green activists step up their agendas (Starbucks, KFC and Coca-Cola are just some of the brands on the recent receiving end). Of course, the situation for brands is a bit different. Along with activist non profits, it’s also their biggest customer, Walmart, now laying down the pressure to be more green.

The difference is that, while it’s pressing for action, Walmart is also extending a hand that’s chock full of solutions. I attended the retailer’s Sustainable Packaging Expo in Bentonville in April, and the environment was entirely unique. Where else can you find a Sam’s Club buyer walking the aisles with her point person from Nestle and talking to packaging material and service providers about solutions (vetted, conveniently by Walmart through third-party review), and then sit in on educational sessions with Walmart insiders about their sustainable wins?

It’s a much friendlier atmosphere to talk sustainability than Walmart first encountered. Regardless, the lesson from Walmart is that there’s a lot that can come from conversation with any kind of partner or critic.

Lee Scott told Fortune conference attendees that it was the act of bringing various disciplines and partners together that spurred most of Walmart’s environmental programs-and it’s the key learning to come from all his efforts in sustainability.

“We’re a better company because we let people from the outside come and work with us,” he told conference attendees.

Once Walmart started listening, he said, the company realized its critics could actually on alone.