Rep. Marsha Blackburn (R-Tenn.) speaks at a news conference in Washington on Feb. 12, 2015. (Andrew Harnik/For The Washington Post)

ANY DOUBT about the kind of investigation into fetal tissue research that would be conducted by a special House panel was erased at its first hearing, when one of the witnesses called by Republicans drew comparisons between this life-saving medical work and the experiments of Nazi war criminal Josef Mengele. And the panel has gone downhill since.

The committee has issued indiscriminate subpoenas, intimidated witnesses and relied on misleading information. It is abusing power at taxpayer expense, and Democrats are right to demand its shutdown. In a letter this week to House Speaker Paul D. Ryan (R-Wis.), 181 of the 188 House Democrats called for disbanding the select investigative panel, characterizing it as a “witch hunt.” The committee was created last year by former speaker John A. Boehner (R-Ohio) to probe connections between abortion providers and medical researchers in the wake of the furor caused by sting videos purporting to show Planned Parenthood involved in the illegal sale of fetal tissue.

As we now know, those videos are bunk, neither accurate nor reliable. Previous investigations by three House committees found no wrongdoing. Twelve states that launched investigations into Planned Parenthood found nothing; another eight determined there was no credible evidence even to warrant investigation. The only wrongdoing, according to a Texas grand jury that was under orders to investigate Planned Parenthood, was committed by the antiabortion activists who filmed the misleading videos.

None of those facts seems to matter to Republicans who see the committee as an opportunity to score political points with their antiabortion base. Their heavy-handed tactics in service of this grotesque theater are disturbing. Rep. Marsha Blackburn (R-Tenn.), the committee chair, despite amassing 19,000 pages of documents claims noncompliance and has unilaterally issued dozens of subpoenas, often without reaching out to subjects to ask for voluntary compliance. Her demand for names of individuals who work in labs and clinics without providing a justification and without assurances of privacy is troubling and irresponsible. According to Democrats, one of the individuals targeted by the investigation already has received graphic death threats after being identified in the videos.

There is no legitimate reason for this inquiry. Individuals and organizations are being unfairly targeted and placed at risk. Mr. Ryan, who took office with talk of wanting to change how the House does business, should put an end to these sordid proceedings.