The politics of blacklisting is again rearing its ugly head.

And what’s driving it is a conviction by some on the left that Donald Trump is so dangerous that his donors need to be spotlighted and exposed.

Except that this time there’s a backlash to the blacklisting. And even liberals are denouncing the move as a horrible, terrible, no-good, really bad idea.

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The latest contretemps was started by Hollywood types, so it has a nice celebrity status to lift it above the usual Twitter talk.

With Trump scheduled to hold a fundraiser in Beverly Hills, Eric McCormack, a star of “Will & Grace,” urged the Hollywood Reporter to reveal whoever has the temerity to show up and support the president’s campaign.

"Hey, @THR, kindly report on everyone attending this event," he wrote, "so the rest of us can be clear about who we don't want to work with. Thx," McCormack tweeted.

His co-star, Debra Messing, who despises Trump, soon echoed the call: “Please print a list of all attendees please. The public has a right to know.”

The president, who has tangled with Messing before, quickly hit back:

“I have not forgotten that when it was announced that I was going to do The Apprentice, and when it then became a big hit, helping NBC’s failed lineup greatly, @DebraMessing came up to me at an Upfront & profusely thanked me, even calling me ‘Sir.’ How times have changed!”

A word about campaign donors: Of course their contributions are public record. But it takes some work to dig up the list of contributors at a particular event or in a certain geographic area—and in this hyperpartisan environment, that’s not done for fun.

But this tale has a twist. Some liberals say the actors went too far.

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On “The View,” Whoopi Goldberg, who’s no Trump fan, delivered a stern condemnation:

“This is not a good idea, okay? Your idea of who you don’t want to work with is your personal business. Do not encourage people to print out lists because the next list that comes out, your name will be on, and then people will be coming after you!”

Whoopi went on to invoke the Hollywood blacklists of the McCarthy era, when plenty of people in the entertainment industry lost their jobs because a mere whisper of communist affiliation. “Nobody cared whether it was true or not,” she said.

Lo and behold, McCormack suddenly started backpedaling.

He said on Instagram that his earlier tweet “has been misinterpreted in a very upsetting way. I absolutely do not support blacklists or discrimination of any kind, as anyone who knows me would attest. I'd simply like to understand where Trump's major donations are coming from, which is a matter of public record.”

This is pure Hollywood fiction. What did McCormack think would happen to those donors whose names would be made public? His original tweet said he wants to know who’s giving Trump cash so he and others “can be clear about who we don't want to work with.” If that isn’t a boycott, what is?

Face it, he’s rewriting the script in a way that no producer would accept.

Messing, also feeling the heat, joined the retreat: “I couldn’t have said it better.”

The same issue surfaced last month when Rep. Joaquin Castro, chairman of his brother’s presidential campaign, published a list of Trump donors in his Texas district and their business affiliations.

The congressman, in the wake of the El Paso shootings, said those who financially support Trump are “fueling a campaign of hate.” But Castro faced a substantial backlash.

House GOP Whip Steve Scalise, who was badly wounded at a baseball practice by a gunman who hated Republicans, said: “People should not be personally targeted for their political views, period.”

There’s a sliding scale here: Refusing to serve people in restaurants. Shouting at them in public places. Organizing protests outside their homes. Publicizing lists of donors. Saying they are fueling “hate.” It’s all aimed at harassing those who participate in democracy, and too many Trump haters seem to justify it when the president, his aides and supporters are the targets.

But the strong criticism of Debra Messing and her Hollywood pals, even by liberals on “The View,” suggests a growing realization that some of these tactics go too far.