When did it become ­acceptable for politicians, and their media helpers, to target private citizens for their ­political opinions? A pair of ­incidents this week ­revealed just how routine such bullying has become.

In the wake of the mass shooting in El Paso, Rep. Joaquin Castro (D-Texas) released the names of a few dozen San Antonio residents who had donated to President Trump’s re-election campaign. (Castro is chairman of the presidential campaign of his twin brother, Julián.)

Castro was apparently unconcerned by the prospect that these people — retirees and small-business owners — would be inevitably targeted for ­harassment. They had voted the wrong way and donated to the wrong campaign, and they needed to be punished.

The right exploded in anger at his action, but the left, with a helpful assist from a complicit mainstream media, pretended this was a perfectly normal thing for an elected official to do. Political ­donations, Castro’s apologists noted, are public information.

Of course, so are divorce records and property sales, but no one would want Trump to be bandying about such information on his Twitter timeline.

As Guy Benson of Townhall noted, if the president tweeted a list of top Democratic donors somewhere in the heartland, including their workplaces, “the media would be in a full-blown, panicked meltdown. You know it, and I know it.”

We all know it. Yet liberals’ hypocrisy went over their own heads.

Liberals view the election of President Trump as a monstrous anomaly, something that should never have happened. They view all Trump supporters, be they Acela Corridor denizens or car-dealership owners in suburban Texas, as complicit in this great evil and therefore fair game.

The media is only too happy to help. Everyone remembers what The Washington Post and The New York Times did to the Covington Catholic boys. Or recall the way CNN went after an anonymous tweeter after Trump retweeted an image he had created mocking the network.

The message to anyone who dares not march in lockstep with liberalism: You don’t matter, and we will target you for ruination whenever we feel like it.

Also this week, news broke that billionaire Stephen Ross was hosting a fundraiser for the president at his Hamptons home. Ross, owner of the Miami Dolphins and owner of the gym franchises Equinox and SoulCycle, as well as many real estate holdings, became an instant target for the crazed anti-Trump mob.

Hollywood actors like Billy Eichner weighed in, with the typical levelheadedness for which liberals are known, accusing Ross of “enabling racism and mass murder.”

Ross is an investor in many businesses, including the new Hudson Yards development. People boycotting his businesses because of his Trump fundraiser are more likely to hurt the regular non-billionaires who work at his gyms and properties than Ross himself.

Nor is such atrocious behavior limited to this side of the Atlantic. Brexit supporters in the United Kingdom face similar abuse from those who believe that a vote to leave the European Union was a vote for racism and xenophobia. It was Remainer extremists who popularized the cruel tactic of splashing Brexiteers with milkshakes; soon the trend crossed the pond and ­arrived on our shores.

Liberals, in short, have ­resolved that anything goes as they seek to thwart and undermine democracy in the name of liberalism.

Sure, liberals always say they want more political participation from the masses, but it turns out the only participation they welcome is the kind that helps them win.

Hence, too, their efforts to use underhanded juridical means to undo the outcome of elections they lose, whether that’s the “collusion” probe in America or endless bureaucratic stalling aimed at preventing Brexit.

But the attacks on private citizens is a new low.

People who choose to be involved in the political world — the elected officials, the talking heads, the writers, the consultants and so on — know what they’re getting into. But people outside “this thing of ours” don’t deserve to have their public ­information exposed because of who they support. They shouldn’t have their businesses decimated and their employees left jobless. Playing this dangerous game with ordinary men and women is downright, well, illiberal.

Twitter: @Karol