Dylann Roof was condemned to death by a Federal jury. It is a just sentence befitting a monster who murdered nine African-Americans in the middle of Bible study at a South Carolina church.

We should feel no guilt for his sentence and have no reservations about carrying out. He deserves to die.

What Roof deserves is our contempt, our vitriol, our hatred.

I declare unreservedly that I hate him and everything he stands for. Why are we so reluctant to declare our hatred for odious, racist murderers? Where is the visceral abhorrence and detestation for monsters?

It wasn’t always thus.

Abraham Lincoln had no hesitation declaring his hatred for the abomination of slavery. In 1854, in Peoria he said, “I cannot but hate slavery. I hate it because of the monstrous injustice of slavery itself.” Churchill said openly that “I hate no man but Hitler.” And because he hated the beast, he inspired a nation to fight him. The French, who did not hate Hitler, collaborated with him and sent Jews to the gas chambers instead.

It seems that hatred has gone out of vogue.

Let my Christian brothers speak of loving one’s enemies. I will confess my admiration for my loving African-American brothers and sisters — many of them family members of Roof’s victims — who came together in South Carolina to forgive the killer after his murderous rampage.

But for all their moral greatness, they are still wrong. We have an obligation to hate evil and never forgive it lest it be permitted to spread. We must fight it instead.

Let my Catholic friends tell me to turn the other cheek. When it comes to racist mass murderers like Roof, I cannot but reject both New Testament teachings and instead embrace Solomon’s proclamation in Proverbs: “The fear of the Lord is to hate evil.” I will welcome what King David said regarding the wicked: “I have hated them with a deep loathing. They are as enemies to me.”

The kind of man who could storm into a church and pump worshippers with bullets is not a man at all. He is a beast, pure and simple. He may once have been created in the image of God. But he has since erased every last vestige of God’s image from his countenance. He is no longer our human brother. He is a bloodthirsty animal.

Loving the victim of a crime generates compassion for suffering. But hating the perpetrators generates action to stop the orgy of murder. While innocence should evoke compassion, evil should evoke only contempt and the determination that it be eradicated.

I am well aware that, right now, Roof elicits contempt. But I have seen time and again how racism, after a time, can slowly once again rear its ugly head. Memory alone cannot inspire a war against racial hatred. It must result from righteous indignation.

Only a true contempt for racist murder and a moral revulsion for the prejudice that inspires it can lead to a commitment to its obliteration.

Those who would forgive Roof, however righteous and noble the motivation, are exhibiting a broken moral compass. And those who say they love him — especially when such love is based on misunderstood teachings in Scripture — have betrayed decency and faith.

We must purge our ourselves of any shred of sympathy which might seek to understand his motives. When it comes to the slaughter of innocents, we must brook no excuse, allow no rationalization, accept no form of justification. Murder is always wrong. Period.

Forgetting how to hate can be just as damaging as forgetting how to love. I realize that immersed as we are in a Christian culture that exhorts us to “turn the other cheek,” this can sound quite absurd. Little do we remember, it seems, the talmudic aphorism that those who are kind to the cruel end up being cruel to the kind.

Indeed, exhortations to hate all manner of evil abound in the Bible. Hatred is a valid emotion — an appropriate response — when directed at the truly evil: those who have gone beyond the pale of human decency by committing acts which unweave the basic fabric of civilized living. Contrary to Christianity which advocates turning the other cheek to belligerence and loving the wicked, Judaism obligates us to despise and resist evil at all costs.

Amid my deep and abiding respect for the Christian faith, I state unequivocally that to love the terrorist who flies a civilian plane into a civilian building or a white supremacist who drags a black man three miles while tied to the back of a car is sinful — not just misguided but immoral. To love evil is itself evil and constitutes a passive form of complicity. Indeed, to show kindness to murderers is to violate the victims again.

The purpose of our hatred is not revenge, but the preservation of justice. I wholeheartedly embrace the example of Simon Wiesenthal, one of the most inspirational men of the 20th century, who devoted his life to the pursuit of justice by not allowing Nazi murderers go to their graves in peace. Only if we hate evil passionately will we summon the determination to fight it fervently. Odd and uncomfortable as it may seem, hatred has its place.

Although they referred to a different era in history, the words of Martin Luther King, Jr. still ring true today: “We will have to repent in this generation not merely for the vitriolic words and actions of the bad people, but for the appalling silence of the good people.”

One of the most frequent themes of my writing is how we — a generation with a 50-percent divorce rate and a professional singles scene — have forgotten how to love. But when it comes to monstrous murderers like Dylann Roof, our biggest impediment might just be that we have forgotten how to hate.

Shmuley Boteach, “America’s Rabbi,” whom the Washington Post calls “the most famous Rabbi in America,” has just published “The Israel Warrior: Standing Up for the Jewish State from Campus to Street Corner.” Follow him on Twitter @RabbiShmuley.