In his bridge-club cords and grandpa shoes, 80-year-old Yvon Chouinard doesn’t look the rock-star entrepreneur.

And, when he speaks, he doesn’t sound much like one either. The founder of US outdoor apparel brand Patagonia believes stock market valuations are “absurd”, investing in shares is “buying blue sky” – and modern-day capitalism is destroying the planet.

“I’d like to see an end to public corporations because we’re not going to revolutionise them, we’re not going to change them,” the self-confessed reluctant businessman told the Guardian.

It is easy to dismiss such comments as sour grapes or market envy. As a private company (Chouinard remains sole owner), Patagonia lacks the investment clout of Nike or The North Face.

Not that that has necessarily restricted the plucky Californian brand, which posted sales revenues of more than $1bn last year.

A soft-spoken former climber hailed by some as the Steve Jobs of eco-conscious commerce, Chouinard is not your usual businessman. Based in the small Californian town of Ventura, he eschews publicity and prefers gardening to board meetings. He set up his first company – a small climbing equipment firm – more than 50 years ago only because no one was selling the kind of pitons he wanted.

Facebook Twitter Pinterest Chouinard with rock climbing equipment. Photograph: Patagonia

In 1973, he established Patagonia to help finance the low-margin equipment firm. Despite Patagonia’s exponential growth, Chouinard insists his company has sought to remain true to its eco-conscious origins. He cites the brand’s decision to use 100% organic cotton in its garments and to donate 10% of its profits (or 1% of sales – whichever is greater) to environmental charities by way of example.

Patagonia is far from perfect, however. By his own admission, the idea of a fully sustainable business or product is impossible: “There is no such thing as sustainability. The best we can do is cause the least amount of harm.”

Instead of “sustainable”, he prefers the term “responsible”, which, he argues, starts with companies treating nature not as a resource to be exploited but as a unique, life-giving entity on which we all – not least business – depend.

Chouinard may have his acolytes among eco-conscious consumers, but he doubts mainstream companies are listening to his reforming message. “I used to think that if we could show that being a responsible business is good business, then others would follow. And some do, but they’re tiny little companies. But the public companies, they’re all green-washing. I have no hope that they’re going to change.”

The Observer profile: Yvon Chouinard Read more

Nor does he hold out much hope for government to force big business to act more responsibly. Politicians are “pawns of corporations” says the man who, together with a coalition of indigenous North American tribes and grassroots groups, is currently suing the Trump administration for attempts to reduce the size of ancestral lands in Utah.

Our best hope for change lies with consumers, Chouinard maintains: “You’ve got to change the consumers first and then the corporations will follow and then government will follow the corporations. They [governments] are last in line.”

Hence, his recent appearance in New York, where Patagonia was premiering a new documentary at the Tribeca film festival about the dangers to wild salmon of fish hatcheries and open-net fish farms.

The film, entitled Artifishal, is intentionally provocative, Chouinard admits. “People don’t read any more and they make decisions based on emotions, so I think film is the best way to elicit people’s emotions.”

Eliciting consumers’ emotions is not without its risks, of course. One of the chief beneficiaries of salmon hatcheries are recreational anglers, a key consumer group for Patagonia. Chouinard says he couldn’t care less: if he loses business, so be it.

“I absolutely don’t believe in doing … focus groups and all that shit. Proctor and Gamble-style, no risk. Just do it,” he says.

The same thinking lay behind his decision in 2011 to run an ad campaign on Black Friday, the busiest day in the US retail calendar, with the tagline: ‘Don’t Buy This Jacket’.

Facebook Twitter Pinterest ‘Change the consumers first,’ says Chouinard. Photograph: Patagonia

But 50 years of activism has seen Chouinard lose as many battles as he has won; high-profile campaigns against ocean pollution and genetically modified food are two notable cases in point.

Failure, fortunately, doesn’t seem to dishearten him. “If you expect victories, then you’re in the wrong business. Evil never stops. And it’s just a matter of endless fighting … the fight is the important thing.”

For all his talk of evil, it would be tempting to think Chouinard was religious. He is not. The money that is being spent on going to Mars “to see if God is up there”, he jokes, would be better spent on “doing some actual good”.

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As he enters his ninth decade, the appetite of this business pioneer to disrupt the status quo appears to be growing, not shrinking.

Sparking his radicalism is the election of populist leaders, such as the US’s Donald Trump and Brazil’s Jair Bolsonaro, whom he accuses of riding roughshod over nature. More important still is the looming threat of climate change and massive species loss. As he told the audience at Tribeca: “The polar bear is toast.”

It’s time for brands to become more vocally political, he argues. Consumers, especially among the young, increasingly expect their favourite brands to speak out, he says.

Chouinard, for one, leaves little doubt where his politics lie. When President Trump announced his decision to slash corporate taxes, for example, Patagonia announced it would give away the money saved.

That added another $10m to its charitable outgoings, bringing to $105m (£80m) the total lifetime amount donated to environmental causes.

Chouinard sees it as an act of “karma”: “After all, we don’t need it, we’re debt-free.”

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Similarly, plans are afoot to jazz up Patagonia’s political advertising. Rather than just call on the US public to vote for the environment, it now intends to specifically endorse pro-conservation candidates, says Chouinard.

“We simply can’t pussyfoot around anymore. We have to just say, you know, this administration is evil and anybody who is denying climate change is evil.”

Such moves will provoke controversy without doubt. Not that Chouinard cares. As he likes to advise graduating students, life is easier if you break the rules rather than conform to them.

“Invent your own game and that way you can always be a winner.”

• This article was updated on May 20 to remove an earlier inaccuracy which stated that Patagonia gained 600,000 new customers and year-on-year sales quadrupled as a result of its 2011 campaign Don’t Buy This Jacket.