Donald Trump’s opponents, which include the entire Democratic Party, progressives of all stripes and even some wet Republicans, are mounting what they call a “resistance” movement against the new administration.

This is not your “loyal opposition” of years past but something new and increasingly ugly. On Thursday, they pulled off their latest sabotage by getting Attorney General Jeff Sessions to recuse himself from an investigation of possible Russian interference in the election. They’re still calling for his head. More on that later.

There’s nothing wrong with tough opposition. Many of us think congressional Republicans were far too easy on Barack Obama and should have pushed back more against his socialist agenda.

But there’s something in between polite (and ineffective) opposition and the kind of outright declaration of war that progressives announced when they learned the GOP had taken not only both houses of Congress but also the White House.

If President Trump’s antagonists are resisting anything, it is the call to civility — the willingness to agree to disagree but to work within the system. Bare-knuckle politics has given way to brass knuckle pounding.

House Minority Leader Nancy Pelosi and Senate Minority Leader Charles Schumer have called for Mr. Sessions to resign because he had met twice with the Russian ambassador last year while serving on the Senate Armed Services Committee and had not mentioned it at his confirmation hearing. The Washington Post got the ball rolling with a breathless story about Mr. Sessions not citing the meetings when asked by Sen. Al Franken, Minnesota Democrat, about “possible contacts between members of President Trump’s campaign and representatives of Moscow.”

Mr. Sessions briefly met Russian Ambassador Sergey Kislyak, among other ambassadors, at a Heritage Foundation forum in July in Cleveland, and once in Mr. Sessions’ Senate office in September. He did so, his office said, as a member of the Armed Services Committee, not as a Trump campaign rep.

As Breitbart’s Joel Pollack notes, “The Post does not provide the full transcript of the question, from Sen. Al Franken, Minnesota Democrat, and Sessions’ answer. Instead it summarizes the exchange in a way that makes it seem that Sessions was asked if there was any contact at all between the campaign and representatives of the Russian government.”

Later, The New York Times joined the posse with similarly, uh, incomplete reporting.

Calling it “fake news,” Mr. Pollack wrote that, “A chance greeting at a public event, and a Senate meeting in the course of his official duties, do not add up to anything, and the full transcript — also omitted by the Times — makes it clear Sessions told the truth.”

After the Post and Times cast Mr. Sessions as a liar who is unfit for office, the calls began for his resignation, and even some Republicans helped the Democrats by calling for Mr. Sessions to recuse himself from DOJ’s Russian probe.

The same news organs had little to say when former Attorney General Eric H. Holder, Jr. was caught lying under oath about his knowledge of the DOJ’s “Fast and Furious” gun-running scandal with Mexican drug dealers, or when several key figures from the Obama Administration, including the president, Secretary of State Hillary Clinton and UN Ambassador Susan Rice lied for two weeks about a video causing the attack on the U.S. consulate in Benghazi on Sept. 11, 2012.

Well, that was then and this is now.

Missouri Democratic Sen. Claire McCaskill called on Mr. Sessions to resign, saying, “I’ve been on the Senate Armed Services Committee for 10 years, and in that time, have had no call from, or meeting with, the Russian ambassador. Ever.” National Review’s Charles C.W. Cooke quickly turned up two tweets from Ms. McCaskill from 2013 and 2015 discussing her meetings with the Russian ambassador. Oops.

Last August, progressives were aghast that Mr. Trump returned rhetorical fire after Khizr Kahn, a Gold Star father of a slain Muslim U.S. soldier, assailed him in a political speech at the Democratic National Convention. But some thought nothing of attacking President Trump for featuring at Tuesday’s speech Carryn Owens, the Gold Star widow of a Navy Seal slain in Yemen, who drew a two-minute standing ovation.

Mr. Trump has been in office for a little over a month, but given the ferocity and dishonesty of his opponents, at least he knows what they’re made of.

Mr. Sessions may think it honorable to step back from the Russian probe, but it’s like throwing chum off the back of a boat and expecting the sharks to eat it and swim away.

As for Mr. Trump, he should forgo the usual Republican strategy of duck and cover, which is a huge reason why he was elected.

• Robert Knight is a senior fellow for the American Civil Rights Union.