The opinions expressed by columnists are their own and do not necessarily represent the views of Townhall.com.

The sadistic treatment of Paul Manafort illustrates something I have believed since I attended graduate school in the 1970s and saw the behavior of left-wing students: Leftism makes people meaner.

There are kind and mean conservatives and kind and mean liberals. Neither liberalism nor conservatism makes people kinder or meaner. But this is not the case with leftism. With the handful of exceptions that accompany every generalization, leftism makes people meaner, even crueler.

Take the transfer of Manafort, the one-time Trump campaign manager, from a federal prison to New York's Rikers Island prison. Rikers Island is universally regarded as a wretched place. As Harvard law professor Alan Dershowitz wrote:

"The decision to move Paul Manafort ... from the decent federal prison to which he was sentenced to solitary confinement to the dangerous hell hole that is New York City's Rikers Island seems abusive and possibly illegal.

"I know Rikers well having spent time there visiting numerous defendants accused of murder and other violent crimes. It is a terrible place that no one should ever be sent to."

Mass murderers and torturers are among those incarcerated at Rikers Island.

Moreover, Manafort, found guilty solely for white-collar crimes, will be placed in solitary confinement -- "for his own safety."

Virtually everyone who has written about solitary confinement, both on the right and the left, deems it torture. Manafort will therefore be tortured after being sentenced to seven years' imprisonment for fraud and, in the words of the Daily Wire, "a little-known law that requires lobbyists to report that they are working on behalf of a foreign government (in Manafort's case, Ukraine)."

Angry over the possibility that Manafort may be pardoned by President Trump, the Manhattan District Attorney, Cyrus Vance, charged Manafort with additional crimes based on state law. That way, if found guilty of state offenses, he cannot be pardoned by Trump, as the president's power to pardon applies only to federal -- not state -- crimes.

Everyone knows this prosecution is politically motivated. Vance hates the president and wants to use solitary confinement in a hellhole with violent criminals to squeeze Manafort into testifying against the president.

As Dershowitz said to me on my radio show, what Vance is doing reminds him of Stalin and Beria -- the infamous state prosecutor, a man Stalin referred to as "my Himmler." Dershowitz, a lifelong liberal Democrat and supporter of Hillary Clinton, does not use Stalin analogies loosely.

To her credit, Alexandria Ocasio-Cortez tweeted: "A prison sentence is not a license for gov torture and human rights violations. That's what solitary confinement is. Manafort should be released, along with all people being held in solitary."

I might add that my opposition to Manafort's treatment is not partisan or new. On a number of occasions over the years, I have cited favorably New York Review of Books articles describing the horror of solitary confinement.

Despite its history of opposition to solitary confinement, The New York Times article reporting the plan to relocate Manafort said nothing against the unnecessary transfer but did comment on the expensive suits Manafort used to wear.

Solitary confinement is "basically a deathtrap," former New York City Police Commissioner Bernard Kerik wrote when Manafort was placed in solitary at his federal prison. Manafort should never have been sentenced to solitary confinement. But Robert Mueller (and Judge Amy Berman Jackson) sought it for the same political reason Vance has: to break the man.

As former federal prosecutor Sidney Powell wrote: "When a witness or defendant from whom prosecutors want 'cooperation' does not do as they demand, they put him in solitary confinement. And it works. It literally breaks people.

"Solitary does have a place in our prison system, but only for those people who are simply too dangerous to be placed around others at all. However, the torture of solitary confinement should never be used as it is now to break people to prosecutors' will -- to torture them until they will say or do anything to get out.

"Solitary is also called the 'hole.' It's a small space, barely large enough to stand, with a slit for light, to which prisoners are confined/caged for 23 hours a day. ...

"Paul Manafort, seventy years old, has endured this torture for eight months. He's now in a wheelchair, while Judge Amy Berman Jackson mocks his rapidly deteriorating health. Where is the outcry from the ACLU?"

So, then, what enables Vance, Mueller and Jackson to engage in such evil?

The only answer is their politics -- the politics of the Trump-hating left. Cyrus Vance, Robert Mueller and Amy Berman Jackson may well be good parents, loving spouses, loyal friends and charitable individuals. But leftism has given them permission to act vilely and mercilessly while thinking of themselves as fine people -- just as evil doctrines have done throughout history.

As noted at the beginning of this column, when I was at Columbia, I witnessed this leftist mean-spiritedness firsthand in the personal cruelty of left-wing agitators against professors and others with whom they differed.

Here's a question perhaps millions of parents will be able to answer: If your child returned home from college a leftist, was he or she a kinder or meaner person than before he or she left for college?

The question is rhetorical.