Summary: Evil must be cleansed; it cannot be cured.
“A single witness shall not suffice against a person for any crime or for any wrong in connection with any offense that he has committed. Only on the evidence of two witnesses or of three witnesses shall a charge be established. If a malicious witness arises to accuse a person of wrongdoing, then both parties to the dispute shall appear before the LORD, before the priests and the judges who are in office in those days. The judges shall inquire diligently, and if the witness is a false witness and has accused his brother falsely, then you shall do to him as he had meant to do to his brother. So you shall purge the evil from your midst. And the rest shall hear and fear, and shall never again commit any such evil among you. Your eye shall not pity. It shall be life for life, eye for eye, tooth for tooth, hand for hand, foot for foot.” 
To the modern mind, evil is a malady to be cured. The mass murderer must be understood and the government must take steps to avoid the undesirable action ever occurring again. The underlying motive driving the thief must be uncovered and addressed so he will not want to steal again. National leaders and the cultural elite feel compelled to discover what drives the Jihadist who slaughters the innocent; and when the mass murderer is caught, we feel compelled to imprison him so that we can cure him. The overarching concept in modern jurisprudence is that evil can be cured. We incarcerate criminals, but the prevailing purpose for incarceration is treatment rather than punishment. However, evil cannot be cured.
Candidly, I am fearful of any government that attempts to cure evil rather than holding miscreants accountable for their acts. The old Soviet Union was a nation of laws—they had a constitution and agreed they would abide by the laws they drafted. Consequently, they boasted of their humane treatment of social deviants. The Duma did not outlaw Christianity; it reclassified it as mental illness. Christians were not executed because of belief in the Son of God—they were sent to mental institutions for treatment in order that they might be “cured” of their illness. It seems a trait of cultures and nations that with time they attempt to regulate faith through coercion, attempting to compel uniformity of thought among the citizenry. Christianity, especially, is targeted because it cannot acknowledge anyone as divine except for God.
After the fall of South Viet Nam, the conquerors from the north did not condemn those who differed on issues of policy with the state, they merely sent them to “re-education camps” where they would gain a new perspective and learn to keep their mouths shut. The northern Communists were disappointed that people spoke of them as uncivilised. “We are civilised,” they argued. “We don’t kill those who disagree with us; we re-educate them.” I suggest that efforts to cure evil are not only destructive, they are cruel in the extreme—they reflect the fallen nature of mankind’s ability to reason.
Despite the best efforts of modern societies to cure evil, it must be stated that evil cannot be cured. To speak of a cure is to assume that the one afflicted will be unchanged save for removal of the offending malady. To speak of curing evil is to assume that evil is merely a flaw in human character, a trifling deficit that has no real long-term consequences. However, evil condemns not only the soul of the person ensnared by evil, but it contaminates all who tolerate its presence.
Understand that evil is an offence to Holy God. Perhaps that is one of the major difficulties in speaking of evil among our contemporaries—we have defined evil down. Evil should be defined as any act or any thought that offends God’s holiness. Because evil is an offence to Him, all evil is wicked. Those who engage in evil are condemned as wicked in the sight of the Lord God. What is required for mankind is not a cure for evil, but a means by which we can put evil away; we require a way to deal with evil.
EVIL IS INVASIVE — The command before us is one of several presented among the Deuteromic laws. To be certain, God’s holy law set a high standard for ancient Israel—God demanded that His ancient people were to be holy. Among the faithful gathered as churches in this day, God still calls His people to be holy. Through Peter, God commands those who would follow Him, “Like the Holy One who called you, become holy yourselves in all your conduct, for it is written, ‘You shall be holy, because I am holy’” [1 PETER 1:15, 16 NET BIBLE]. God’s holiness was emphasised in decisive fashion during the days of wilderness wandering. In the Book of Deuteronomy, the LORD says repeatedly, “You shall purge the evil from among you.”