Why do some Evangelical Christians act in ways that reinforce some of the worst stereotypes propagated by their critics? Take Jerry Falwell Jr., president of Liberty University, which claims to be the largest Christian University in the world. Falwell, together with the Reverend Robert Jeffress, a pastor and televangelist, has been among Donald Trump’s most enthusiastic Evangelical cheerleaders.

How enthusiastic? In his recent opinion piece in the Washington Post, Falwell called Trump a “leader with qualities that resemble those of Winston Churchill” — demonstrating a staggering historical ignorance about Churchill and a stunning blindness about Trump.

Winston Churchill was arguably the greatest orator of the 20th century; in the 21st, Trump is among the most banal. Churchill possessed extraordinary knowledge of history and policy; Trump is the most ignorant major-party candidate in U.S. history. Churchill was extraordinarily prepared to become prime minister; Trump would be the least qualified American president ever.

Falwell’s analysis is sloppy and shoddy. For example, he complains about the $19 trillion national debt while failing to note that, under a President Trump, it would explode. Trump has gone out of his way to criticize those who want to reform entitlement programs, which is the great driver of our debt. He’s promised to double (to $500 billion) the amount Hillary Clinton will spend on infrastructure. And his tax proposal would drain trillions from the Treasury. There is nothing in Mr. Trump’s agenda to suggest that he has any interest in “less government.”

The president of Liberty University also said Trump will “take the battle to that enemy [ISIS].” But as recently as last fall, when the Islamic State controlled larger areas in Syria and Iraq than it does today, Trump was saying that ISIS was not ours to take on and that we should “let Russia fight it.” That is hardly taking the battle to the enemy. Trump now says he would declare war on ISIS but wage it with “very few troops.” We’d win the war with “unbelievable intelligence.” As usual with Trump, one should put the emphasis on “unbelievable.”

Falwell blames the “feckless Republican establishment” for, among other things, allowing President Obama to draw and then quickly erase a red line in Syria, even though Congress has no role in that decision and had no means to prevent the president from doing what he did.

Trump clearly has a disordered personality — unstable, obsessive, vindictive, narcissistic, cruel, and apparently lacking empathy. Rather than acknowledge it, Falwell demands that Republicans “stop whining about Trump’s temperament,” as if the problem were not Trump’s temperament but the concerns raised about it.

Falwell praises Trump for his “kindness” and “generosity.” What a curious way to refer to a man who has mocked a former prisoner of war, the grieving mother of a war hero, and a reporter with a physical disability. Trump likened Ben Carson’s “pathology” to that of a child molester, ridiculed Carly Fiorina’s looks, made menstruation jokes about Megyn Kelly, called her a “bimbo,” and called women in general “fat pigs,” “dogs,” “slobs,” and “disgusting animals.” He humiliated his first wife by engaging in a very public affair. As for his purported generosity, we know he lies about his charitable giving.

But even that’s not the worst of it. According to Falwell, “We have lived through nearly eight years of weak leadership from a president who did not sign the charter to create the Islamic State but whose policies had the intended or unintended effect (we will be debating that for decades) of breathing life into the lungs of the terrorist group” (emphasis added).

It is one thing to argue, as I and many others have, that the president’s policies were wrong and contributed to the rise of ISIS; it’s something else again to say that he acted with malice aforethought. To suggest that President Obama’s intent may have been to breathe “life into the lungs of a terrorist group” is to accuse him of treachery. That is calumny.

Falwell has fallen under the dark spell of Donald Trump. That is not a crime, but it is having a corrosive effect on his intellectual and moral judgment. He is saying witless and defamatory things. For those of us of the Christian faith, the fact that Falwell is viewed by many as an Evangelical leader makes it that much worse. We have been pained by the harm that a previous generation did to Christian public witness because of partisan, reckless, and graceless comments. Now we have this.

When a leader of a major Christian institution speaks out on public affairs as Falwell has, he is speaking not just for himself. He is making a broader statement about faith and politics – and, in this case, is shaping how people view Christians and Christianity.

One might hope that when people who are so publicly identified as Christians enter the public square, they would bring to it certain distinctives, including a commitment to justice, to treating people, including and especially the weak and vulnerable, with dignity and respect, speaking truth to the powerful instead of acting as courtiers to them, neither slandering opponents nor placing trust in princes, and not allowing the Christian faith to be used as a blunt, political weapon.

In A Severe Mercy, Sheldon Vanauken recounted his days in the anti-war movement during the Vietnam era. “I was one of those caught up in the mood and action of the 1960s,” he wrote.

Christ, I thought, would surely have me oppose what appeared an unjust war. But the Movement, whatever its ideals, did a good deal of hating. And Christ, gradually, was pushed to the rear: Movement goals, not God, became first, in fact — not only for me but for other Christians involved, including priests. I now think that making God secondary (which in the end is to make Him nothing) is, quite simply, the mortal danger in social action, especially in view of the marked intimations of virtue — even arrogant virtue — that often perilously accompany it.

In his private life, Falwell may be a devout man, but in his role as Donald Trump’s flatterer, defender, and attack dog, he has pushed Christ to the rear. His politics are damaging his public Christian witness. They are injurious to the faith to which he has proclaimed his allegiance.

Those who care for Jerry Falwell Jr. and for the institution he represents should intercede on his behalf. His embarrassing and unfortunate act needs to end.

Peter Wehner is a senior fellow at the Ethics and Public Policy Center and a contributing opinion writer for the New York Times.