People try to comfort a Pakistani Christian mother at the funeral of her two daughters, killed in a suicide bombing Sunday, in Lahore, Pakistan, on Thursday. (K.M. Chaudary/Associated Press)

PAKISTAN HAS made progress in fighting terrorism in the past two years, but a horrific suicide bombing in one of its heartland cities on Sunday showed how serious the threat remains. A militant dispatched by an offshoot of the Pakistani Taliban attacked a crowd of families in Lahore who were peacefully strolling in a park on Easter; the group later said Christians were its target. In the end, more than 70 people were killed, the majority of them Muslim, including some 30 children.

Since a 2014 attack on a school that left more than 150 dead, the Pakistani government — and more importantly, its military — has finally begun to fight in earnest against domestic jihadists. But the latest attack exposes the gaps in the campaign. A long-overdue army offensive destroyed Taliban bases in the western frontier territories, forcing many of the militants into eastern Afghanistan. Progress was also made in combating terrorists in the southern city of Karachi. Last year saw a noticeable reduction in successful attacks.

Pakistani authorities largely neglected militant groups deployed in other parts of the country, however, including in populous Punjab province, where Lahore is located. They have also shrunk from measures needed to protect religious minorities, including Pakistani Christians, who number more than 2 million. A poisonous blasphemy law, which provides the death penalty for perceived insults to Islam, remains in force and is regularly used to target Christians.

Pakistan’s failings are hardly unique: Christians are in danger of being eliminated as a significant minority community across the Middle East. Al-Qaeda and the Islamic State, like the Taliban, have adopted the genocidal aim of killing all non-Muslims, a departure from Islamic law as well as centuries of practical coexistence. Christians are being systematically driven out of Iraq, and communities in Syria, Lebanon, Egypt and the Palestinian territories are shrinking as refugees flee to the West. Even as President Obama and responsible leaders in Europe try to fight prejudice against Muslims, Muslim governments are fueling demagogues such as Donald Trump by failing to protect Christians.

Following the attack in Lahore, Pakistani Prime Minister Nawaz Sharif vowed in a televised address to fight terrorism “until it is rooted out from our society,” and authorities arrested hundreds of suspected militants. But the government faces formidable opposition: In Islamabad, thousands of demonstrators this week protested the execution of an extremist convicted of assassinating a governor who criticized the blasphemy law.

The best approach, as Pakistan should have learned by now, is not to tolerate or negotiate with such extremists, but to forcefully confront them. Exceptions cannot be made for jihadists who fight for causes favored by the Pakistani elite, such as the “liberation” of Kashmir from Indian rule, or Taliban battling the Afghan government. While Mr. Sharif and the military leadership have come a long way toward accepting those tenets, they have not yet fully embraced them. That means terrorism will remain a threat to Pakistan for the foreseeable future.