Attorney General William Barr is looking into the murky origins of the politically charged Justice Department investigations that have roiled American public life for the last three years.

Just how did the FBI's "Crossfire Hurricane" investigation into the 2016 Trump presidential campaign get started? What led the FBI to look into whether President Trump was working on behalf of Russia? Why did the Justice Department use an ancient, never-enforced law as a pretext to interrogate then-national security adviser Michael Flynn, leading to one of the most troubling court cases in recent years? And more.

Each investigation involved highly publicized leaks that led to many headlines and endless discussion on cable TV. Anti-Trump voices stood firmly in support of more and more detailed inquiries of the president and his allies.

But now, as Barr looks into how it all started, some voices that were part of that frenzy are changing their tune about the value of investigations. They now express concern about investigations, concern that Barr is politicizing the Justice Department to go after perceived political enemies.

"The power to investigate is the power to destroy," a former U.S. attorney, Gregory Brower, told the Washington Post recently. "The ability to simply point to a pending investigation against a person can have devastating effects on that person and can have a potential political benefit to the person orchestrating the investigation."

"President Trump appears to be now using [his] power, with an assist from the Justice Department, to exact revenge on some perceived political enemies," said NBC's Chuck Todd.

The president is "weaponizing the Department of Justice against perceived enemies," said CNN's Anderson Cooper.

Not to be too blunt about it, but where were these voices the last three years?

Where were they when the Steele dossier burst onto the scene in January 2017, with its extremely damaging and unsupported allegations, leaked to undermine the president right as he took office?

Where were they when the public learned that the FBI, using false information, wiretapped a low-level former Trump foreign policy adviser, Carter Page, giving it entree into some of the campaign's communications?

Where were they when the Justice Department cooked up the idea that Flynn had violated the Logan Act, the 1799 law under which no one has ever been convicted, as a reason to question Flynn? And where were they when officials bragged about going outside channels to grab a chat with a busy, distracted Flynn, and later used that as the basis for a false statement charge even though investigators did not believe Flynn actually lied?

Somebody was using the Justice Department to go after perceived political enemies. And when that person did, the investigations stretched into months, and then years, expanding as time passed.

As Brower said, the inquiries had devastating effects on the people investigated; just ask Flynn or Page or another former low-level Trump campaign aide, George Papadopoulos. They have paid a high price, in both money and reputation, for running afoul of the investigative apparatus.

Also, as Brower said, the investigations were a potential political benefit for the people orchestrating them. Just ask virtually any Democrat on Capitol Hill.

But none of that was much of a concern to the combination of opposition politicians, resistance and Never Trump activists, and a go-along press that fed the investigation machine since before Trump took office. The targets were figures unpopular with Democrats and many in the media.

But now, as Barr seeks to shine a light on how the investigation machine revved up, we suddenly hear concerns about the costs of such investigations.

Former FBI No. 2 and current CNN commentator Andrew McCabe played a role in the excesses we now associate with the Trump-Russia investigation. Now, though, he is complaining about the Justice Department's internal investigation into whether he lied under oath to agents seeking the source of a high-level leak. The source was McCabe himself, but he denied it multiple times. The Justice Department, facing an uphill battle trying a case before a deeply anti-Trump District of Columbia jury, recently decided against charging McCabe. And now, McCabe is indignant about the treatment meted out to investigative targets.

He is particularly angry that the investigation took a long time. "It's just an absolute disgrace that they let this thing drag on as long as they did," McCabe said on CNN, "and put my family through what we've gone through over the last two years ... I'm just disgusted at the way the whole thing has been handled."

An investigation lasting seemingly forever and putting one's family through hell? Imagine that! Coming from McCabe, the lack of self-awareness is so pronounced that it would be darkly funny, were not the events of the last three years so serious.

More complaints are sure to come as Barr, and Barr's appointees, investigate the questionable acts of the investigators. Yes, it will be painful for some. But the public deserves to know what happened.