The movement has sparked outrage in Spain, where the government demanded a crackdown on what it called a violation of the European Union’s free trade rules. Spanish producers also say the actions distract from graver threats to Europe’s wine industry, including Britain’s decision to leave the European Union, which could slow exports to the bloc’s biggest buyer of European wines.
And as the United States under President Trump pivots toward protectionism, European winemakers are expected to face stiff competition from Australia and other countries as the European Union seeks new trade deals to compensate.
While France often conjures the image of well-to-do winemakers in regal chateaus, many are small struggling vignerons, especially in this region, otherwise known as the Pays d’Oc, which built its industry for over a century on low-cost table wines.
These vignerons say they are facing unfair competition, especially from Spain, where a now-fading economic crisis had slashed wine prices. European rules, they insist, deepen their woes by requiring free movement of goods that sometimes don’t meet production or quality standards in the importing country. European Union labeling standards also make it easy for retailers to pass foreign products off as French — a problem that plagues other European countries with their products.
Wine rebels have executed dozens of attacks in protest since last summer, including ambushing Spanish wine trucks at the border and dumping the payload on highways.
The most aggressive rebels are part of a secret commando organization that targeted businesses like Mr. Vergnes’s, which had brokered a handful of Spanish wine contracts for French clients.
“Many people are just scraping by, but no one is listening,” said Lionel Puech, a co-president of the Young Farmers Association, a union that has admitted to joining some of the militant actions, none of which have yet resulted in prosecutions.
France has sought to calm nerves. Last month, the government held a meeting of French and Spanish wine representatives and ministers. They condemned the violence and agreed to strengthen relations.
In Languedoc territory, where vineyards stretch from the Rhône Valley to the Spanish border, such statements make little difference.
While some local wineries have invested in higher-quality products, many vignerons still produce inexpensive table wine for the budget-conscious market.
But with labor costs and taxes nearly twice as high as those in Spain, French producers struggle to compete on price. France also imposes strict grape growing regulations that are more costly to follow than rules in Spain and other European countries.
“Spanish wine doesn’t conform to our rules, but the E.U. requires us to accept it,” said Mr. Puech, who owns a small vineyard in La Rouvière, a village north of Nîmes. “The E.U. is proving to be a hollow shell,” he said. “It creates competitive disadvantages within the single market.”
Spanish wine producers see that argument as an excuse for protectionism. “We can produce the wine at lower cost because salaries are less,” said Juan Corbalán García, who represents the Agri-Food Cooperatives in Brussels. “But that doesn’t mean we’re doing unfair competition.”
Yet when everything is tallied, small Languedoc vignerons take home little more than France’s monthly minimum wage. Even that can quickly turn negative if a harvest is poor or retailers cut orders.
The region was just starting to recover from a decade-old production crisis that pushed some winemakers into bankruptcy — and a handful into suicide — when harvests were hit again in 2015.
This time, wine merchants and brokers like Mr. Vergnes turned to Spain to fill the shortfall. When the harvest rebounded, Languedoc producers were stuck with vast amounts of unsold wine.
The winegrowers thought orders would resume when Spanish stock ran out. But French retailers were getting a hefty margin from selling Spanish wines. Last year, France became the biggest importer of bulk wines from Spain, according to FranceAgriMer, a French agricultural agency.
Languedoc vintners revolted.
Thousands demonstrated, petitioning the government to even the playing field by reducing taxes and regulatory costs. Unions met with retailers to demand more-visible country-of-origin labeling.
When the meetings produced no results, vignerons took matters into their own hands.
Mr. Puech and other activists smashed thousands of bottles at retailers like Carrefour, which carried cheap Spanish wines made to look French, with pictures of chateaus and lavender fields, and selling them at the same price as the competing Languedoc fare, creating sizable margins for the retailers.
The Comité Régional d’Action Viticole, a radical group that goes by the acronym CRAV, also sprang into action. Known for violent actions that have included dynamiting some targets, it has operated underground in Languedoc for over a century, resurfacing when fresh financial hardship hits winegrowers.
A group of CRAV commandos in July 2016 ransacked a large French wine cooperative, Vinadeis, that had bought Spanish wine stocks, smashing the offices with bats and axes, then setting them ablaze. They also claimed responsibility for emptying a flood of wine from Biron, another large Languedoc distributor, to call attention to their problems. The actions are under police investigation.
One CRAV vigilante, a Languedoc winegrower who insisted on anonymity, citing the police investigation, said people had been pushed to their limits. He added that activists were halting their actions for now, but could resume if things didn’t improve.
The winegrower said he had seen his father and other Languedoc families fall into a debilitating debt spiral during earlier wine crises, and wanted to head off new hardship.
“I’m not doing this for pleasure,” he said of his participation in the raids. “But in the global system, it’s always those at the bottom of the ladder who suffer. We want to be heard.”
Mr. Vergnes was still reeling from the impact that message had on his business. But as a native of the area, he admitted it resonated.
In addition to halting deals with Spain (“I have a family to think of,” he said), Mr. Vergnes is ordering new labels for Languedoc wines festooned with the “Made in France” logo. Local distributors are discussing better traceability information for wines to educate consumers about quality, he said. Carrefour and other big retailers have also agreed to buy more Languedoc wine, give them prominent display and clearly mark foreign ones.
“Languedoc has always been a hot-blooded place,” Mr. Vergnes said.
“But I can understand that they are in a crisis,” he added. “If they hadn’t done all this, would things really change?”