A guy walks into a bar.

He catches a few songs by the band, likes what he hears, then approaches the singer when the band takes a break.

“What kind of music is that? Would you call it alt-country?” the guy asks.

“I don’t know, I’m not really into labels,” the singer says.

“Well, I only like alt-country. So I guess I’m not listening to your band anymore,” the guy responds.

It’s a ridiculous scenario, right? But not much more ridiculous than the response that greeted former U.S. Rep. — and possible 2020 presidential contender — Beto O’Rourke after his final congressional town hall in El Paso on December 14.

When asked if he would classify himself as a progressive, O’Rourke responded with a polite but adamant don’t-box-me-in rejection of the question’s premise

“I don’t know,” he said. “I’m not big on labels. I don’t get all fired up about party or classifying or defining people based on a label or a group. I’m for everyone.”

The statement drew immediate howls of disdain from the Bernie Sanders wing of the Democratic Party, which had been gunning for O’Rourke ever since he began offering hints — in the wake of his remarkably close loss to U.S. Sen. Ted Cruz in the November 6 midterms — that he might be willing to launch a presidential campaign.

Sanders loyalist David Sirota already had unleashed an anti-O’Rourke tweet storm, including the assertion that the El Paso Democrat was “the #2 recipient of oil/gas industry campaign cash in the entire Congress.”

The allegation was particularly stinging because O’Rourke got considerable mileage during his Senate campaign from his refusal to accept any money from political action committees.

Sirota’s point was true only if you considered “oil/gas industry campaign cash” to include donations from any employee of a fossil-fuel business. By that standard, if O’Rourke (or any candidate) accepts a $100 donation from someone who happens to work as a secretary for an oil company, he’s tainted.

Let’s not stop there. Let’s make sure candidates don’t take any donations from restaurant employees in New York’s financial district, because we can’t let them get away with accepting cash from Wall Street.

Bernie-ites also made an issue of the notion that O’Rourke “voted with” President Donald Trump 30 percent of the time in Congress.

Presumably, O’Rourke should have voted against expanding private care options for veterans, funding school-violence prevention or making targeted attacks on law enforcement officers a federal crime, simply because the Republican in the White House happened to support those measures. (For perspective, San Antonio-based Democratic Congressman Joaquin Castro also voted for those bills.)

All of this rhetorical nonsense simply validates O’Rourke’s reluctance to accept ideological labels. In the same way that any self-respecting musician would want their work to be heard and assessed for what is being expressed, rather than what genre gets attached to it, O’Rourke wants his message to avoid the prism of mindless stereotyping.

Besides, the term “progressive,” just like “moderate” or “conservative,” has been rendered nearly meaningless. It’s all in the eye of the beholder.

Does “progressive” mean that you support universal health care, comprehensive immigration reform, universal background checks and an assault-weapons ban, climate-change regulations and criminal-justice reform? If so, O’Rourke checks all those boxes.

If it means that you have to meet some Bernie-ite purity-test standard, the question becomes more complicated. For example, the Sanders standard dictates that anything short of complete support for Medicare for All basically makes you a corporate shill.

Medicare for All is a nice concept, but it will also carry an outrageously high (possibly prohibitively high) price tag. Various studies have concluded that it would cost somewhere between $24.7 and $34.7 trillion over its first 10 years. Democrats need to have a serious conversation over the next two years about what that will mean.

It’s to O’Rourke’s credit that during the 2018 Senate campaign he generally maintained an open mind about different ways of getting to universal coverage — including a public option for the Obamacare insurance exchanges and a Medicare buy-in for people who’ve reached the age of 55.

In fact, O’Rourke’s worst debate moment against Cruz came when he half-heartedly suggested that a modest hike in the corporate tax rate could fund Medicare for All, a bit of dubious math that Cruz rightly mocked.

During the 2018 campaign, we heard from Texas Republicans that O’Rourke was too stubbornly leftist for his own good. Now we’re hearing from the left flank of the Democratic Party that he’s a conservative in disguise.

They can’t both be right.

Gilbert Garcia is a columnist covering the San Antonio and Bexar County area. Read him on our free site, mySA.com, and on our subscriber site, ExpressNews.com. | ggarcia@express-news.net | Twitter: @gilgamesh470