President Trump kicked over a hornet’s nest by imposing a 90-day ban on immigration from selected Muslim countries in keeping with his campaign pledges. Andrew McCarthy, the federal prosecutor who convicted the blind sheikh and his accomplices of the first World Trade Center bombing, explains why the ban is legal–despite a federal judge’s restraining order against implementation of the order. I’ll leave it to the legal experts to explain why this is yet another outrageous abuse of power by the judiciary.

The legal issues will be sorted out soon enough. It’s the right policy, despite liberal whining and some conservative complaints.

The liberals claim that the immigration halt will convince Muslims that the U.S. administration isn’t fighting ISIS and other terrorists, but Muslims as a religious group. Some conservatives, e.g. Walter Russell Mead, call it “callous.” The latter characterization is misleading. It is callous towards individual Muslims but merciful to American citizens, who have the right to go about their business without fear of mass terrorist attacks. In Europe, the elites accept a certain level of terrorism as the cost of doing business, and the people grudgingly accept it. Americans don’t see why they should sacrifice their safety or sense of security to accommodate the hurt feelings of other people. Prof. Mead compares this to America’s refusal to accept Jewish immigrants during the Holocaust. I respect Mead, but I find the comparison offensive: How many Jewish refugees from Hitler murdered civilians at random (the answer is, not one)?

As for the argument that the measure will alienate Muslims, precisely the opposite is true. Many Muslim governments, institutions, and individuals do not actively support terrorism, but tolerate it. Active terrorists are a small minority, but they swim in a sea of broader Muslim opinion that sympathizes with terrorists like Hamas in Gaza or Hezbollah in Lebanon.

The last time the Pew Institute surveyed Muslim opinion about Hezbollah and Hamas (in 2010), it found majorities or very large minorities in support of these terrorists in most of the largest Muslim countries. In the United States, the Council on American-Islamic Relations (CAIR)–founded by the pro-Hamas Islamic Association for Palestine–routinely denounces acts of terror on American soil, but has never once criticized Hamas terrorism in the Middle East.

The Obama administration and the Bush administration hoped to persuade Islamist extremists like the Muslim Brotherhood (of which Hamas is the Palestinian branch) to change their spots and turn peaceful. That didn’t work.

The alternative is to serve notice on Muslim governments: If they don’t crack down on terrorists and their supporters, we won’t let their citizens into the United States until we find ways to vet entrants ourselves.

The terrorists have been winning the intelligence war because a very large number of Muslims fear the terrorists more than they do the counterterrorism efforts of the United States and other Western governments. The terrorists infest Muslim communities and operate like a gangland protection racket. It is dangerous to stand up to them. This will change when Muslims fear the U.S. government more than they fear the terrorists.

Is that cruel? Of course. The world is cruel, but its cruelty is not of our making. The first duty of the U.S. government is to show kindness to prospective American victims of terrorism. And it’s great to have a president with the guts to do something about it.