Truth be told, Christopher Walken has always worn his pants grandpa-high, his hats a little out-of-date. And he’s always grown a mean goatee, even in his silvery “legend of the cinema” years.

So it’s no stretch thinking of him as a grandfatherly Saskatchewan canola farmer getting his back up when pushed around by Big Ag in “Percy vs. Goliath,” a plucky, earnest and winning Canadian drama about One Man vs. Monsanto.

It’s funny how movies often go timid when depicting the wrongdoings of running-amok capitalism, changing the names of chemical, mining, fracking, banking or other gigantic entities.

But not Monsanto. Inundated with TV appeals from lawyers carrying on class action suits against the deadly weed killer Roundup, body blows landed by everyone from John Oliver to “60 Minutes,” they’re widely seen as a too-big/too-heavy-handed/too callous villain, and not just in the United States.

“Percy vs. Goliath” is based on the true story of a 73 year-old farmer sued by the company when its genetically modified canola seeds, designed to resist dying when fields are sprayed with Monsanto’s planet-poisoning Roundup, turned up in his crops.

Percy Schmeiser faced unsympathetic judges, shunning by his fellow farmers and a less-than-understanding media — at least at first and at least according to this script — when he was taken to court over patent infringement.

Environmental groups the world over were sounding the alarm over a behemoth of a company acquiring a patented, genetically-modified monopoly over the food people in every corner of the planet need to survive.

Percy was the grandson of “seed savers,” meticulous farmers going back generations, men who noted which fields produced the healthiest plants, keeping records and saving the best producing seeds going back decades to naturally select what worked best for them on the Schmeiser Grangeland farm.

And just by his casting, you know a threatening letter from Big Ag is going to get Walken, playing Percy, riled. His wife (Roberta Maxwell) backs him, as does his fellow farmer who sometimes pitches in as a hired hand (Adam Beach). There’s nothing for it but to pay a local lawyer (Zach Braff) leery of taking on a multinational corporation with bottomless pockets, endless resources, intimidating “investigators” and much higher-priced lawyers (Martin Donovan plays lead counsel for the bad guys). Using “seeds without a license?” Settle.

So that’s your advice, “offer them a fortune for sending me a nasty letter?”

Nope. Court it is, no matter how long the odds. Christina Ricci plays an environmental group recruiter who wants to back Percy, get the press on their side, if she can make Percy see his “precedent setting” case as one with implications for farmers all over the planet.

Clark Johnson’s film, based on a script by Garfield Lindsay Miller and Hilary Pryor, paints Percy as a maverick, a hustling small businessman who bails out of church if it looks like rain will damage crops he cannily got in the ground before his neighbors.

As Percy profits from his industry, maybe his neighbors resent the guy with the new combine, purchased by the premium price he gets for his first-to-market harvest. Maybe that’s why they turn on him.

“You know I’m not a thief, right?”

The arc of this story is how an inherently conservative man, who thinks “I just need to talk to Monsanto” to solve this “personal problem” or “mix-up,” is bullied, harassed and radicalized into a spokesman for a sacred profession, feeding the world. We see Percy turn into a compelling public speaker, and he sees how far-reaching his quixotic legal battle is when he speaks to a conference in India and visits a farm village there.

“Percy vs. Goliath” is dramatically flat, predictable in its pluck at times. But Walken is magnificent, and the other casting — on the nose as it is (Ricci can still pull off the young activist willing to sleep in her car for the cause) — works.

As this film and the earlier documentary on Percy’s struggle make clear, the villain here is faceless. With Monsanto we never need to see bad guys twirling their mustaches over today’s planned intimidation and shortsighted high-handedness. Thanks to guys like Percy Schmeiser, even farmers are starting to get it.

MPA Rating: PG-13 for some thematic elements 

Cast: Christopher Walken, Roberta Maxwell, Christina Ricci, Zach Braff and Martin Donovan.

Credits: Directed by Clark Johnson, script by Garfield Lindsay Miller, Hilary Pryor. A Saban Films release.

Running time: 1:39