For the four years that President Trump occupied the White House, the Democrats positioned themselves as the party that defended the press from a president who delighted in skewering reporters.

On Thursday that narrative flipped. At a hearing of the House Select Subcommittee on the Weaponization of Government, Democratic lawmakers attacked the motives and character of two journalists called as witnesses, Matt Taibbi and Michael Shellenberger.

Messrs. Taibbi and Shellenberger were two of a handful of journalists given access to the internal files of Twitter late last year. 

Their scoops disclosed a vast partnership between the social media platform and the federal government when it came to content moderation.

Other stories from Twitter’s internal files explained in detail how the company would limit the reach of tweets from accounts that it deemed as a threat to spread medical or electoral misinformation, even when the tweets in question were accurate.

One might think the legislative branch would be interested in the executive branch’s role in banning and throttling online speech. The Democrats on the committee though were more interested in impeaching the credibility of the journalists who did the reporting.

In her opening statement, the subcommittee’s ranking member, Representative Stacey Plaskett, accused Messrs. Taibbi and Shellenberger of harming people with their reporting, and referred to them as “so-called journalists.”

Representative Debbie Wasserman-Schultz laid into Mr. Taibbi, claiming that his appearance as a witness before the Republican led committee, “casts a cloud over his objectivity.”

The Congresswoman went further. She then claimed that Mr. Taibbi’s decision to accept access to Twitter’s internal files meant that he was accepting cherry-picked information from a biased source. And during her questioning, she did not allow him to answer the charges.

In an exchange between Mr. Taibbi and Representative Sylvia Garcia, the Democratic member of Congress asserted that Mr. Taibbi’s decision to submit his most recent tweet thread in his TwitterFiles reporting to the committee as his opening statement disclosed his bias against the Democrats.

The most galling exchange was between Mr. Taibbi and Ms. Plaskett. She pressed him over and again to reveal the sources at Twitter who made certain files available to him and Mr. Taibbi repeatedly declined because the sources were confidential.

The behavior of Democrats on the committee Thursday is part of a gradual evolution for a political party that historically defended the principle of free speech and the First Amendment.

Since Mr. Trump won the 2016 presidential election, Democrats have pressured social media companies to remove alleged disinformation and misinformation from their platforms.

During the first impeachment hearings in the House of Mr. Trump, the chief manager, Representative Adam Schiff, published the communications between journalists and members of Congress in his committee’s impeachment report.

Mr. Taibbi reported in January that Mr. Schiff’s office was in frequent contact with Twitter to request the company remove tweets and accounts that it disfavored. 

His office in 2020 urged Twitter to remove the account of New York Post columnist, Paul Sperry. Twitter, in the end, did not comply.