A worshiper in a mosque where hundreds are praying welcomes an obvious newcomer not by asking who he is but with the greeting, “Hello, brother,” just before he is shot and killed.

Eighteen years earlier, Muslims fly passenger jets into the World Trade Center and the Pentagon, killing more than 3,000 Americans.

Who is the true Muslim?

That question came into sharp relief again last Friday with the massacre of 50 Muslims in two New Zealand mosques by a “white nationalist.” It should not be difficult to answer. There are 1.8 billion Muslims, second only to the 2.3 billion Christians. It should be ridiculous to believe that all of them are terrorists but, essentially, that is how some people see them. Those people embrace the fantasy that Muslims plan to Islamicize Western civilization by violence and mass migration masquerading as a refugee crisis.

There is indeed a confrontation involving Muslims but it is one in which they are the victims. The United Nations has called for Myanmar’s military leaders to be tried for war crimes over the treatment of the Rohingya. Syria is locked in a civil war. Saudi Arabia and the United Arab Emirates are bombing Yemen back to the Stone Age.

Afghanistan, Iraq and Libya are in deep travail after being destabilized by the West.

Serbia launched a genocidal war on Bosnia. Israel maintains a lopsided confrontation with the Palestinians. China is holding probably a million Uighurs in “education centers.” The U.S. is engaged in a “forever war” against terrorists, mainly Muslims, with the probably unintended consequence of emboldening extremist Muslims who are slaughtering other Muslims, as in Nigeria and Somalia. In the U.S.

and elsewhere, harassment and abuse are the norm for many Muslims.

Still, Muslims who seek refuge in or migrate to the U.S. and elsewhere are searching for a better life, as did the early English settlers, not to replace their adopted homelands with the brutal tyranny and chaos they left behind. Like this writer, they are grateful they live in the greatest democracy the world has ever known.

Why, then, are Muslims so demonized? Because extremists have given the impression that every Muslim is a potential terrorist and the only way they can prove otherwise is by spying on their neighbors, being supremely exemplary citizens and being willing to forgo their religious identity, at least in public.

But Muslims are not the only targets of hate-filled violence. On June 17, 2015, nine members of the Emanuel African Methodist Episcopal Church in Charleston, S.C., were killed by a man who went in and joined their Bible study group before opening fire. Last Oct. 17, 11 worshipers at the Tree of Life Congregation synagogue in Pittsburgh and were shot dead.

Offering her view on what makes for such tragedies, U.S. Rep. Alexandria Ocasio-Cortez, D-NY, tweeted: “Isolation, believing stereotypes, hysterical conspiracy theories & hatred eventually lead to the anarchy of violence.” But not to be discounted are the enablers, men and women in the media who spout warnings of a white Armageddon as they seek television, book and column gigs that earn them millions of dollars, and unscrupulous politicians who also traffic in xenophobia.

There are those who are dedicated to “cleansing” the U.S. and Europe of all who are not white. As the New Zealand murderer has shown, they have their own ways of communicating online, their own literature, music and symbols and their community is international. Many European nations, weighed down by the burden of their generosity of spirit towards refugees, are struggling to retain their identities in the face of such crisis.

At a different time, they could look to the United States for guidance but now this is where the ethno-warriors turn to for validation. President Donald Trump, commenting on the Charlottesville, Va., protests by white nationalists, said “there were some fine people on both sides.”

He imposed an immigration ban on citizens of Iran, Libya, Somalia, Syria and Yemen – a total of 144.6 million Muslims.

Commenting after the New Zealand tragedy, he said white nationalism is “not a rising threat.” He described white nationalists as “a small group of people that have very, very serious problems, I guess.”

The accused New Zealand shooter, in a manifesto he posted online just before he went on his killing spree, asked himself, “Were/are you a supporter of Donald Trump?” He answered himself, “As a symbol of renewed white identity and common purpose? Sure.”

There is indeed a national emergency but it is not at the southern border.

The genie is out of the bottle and will not go back in. The response lies not so much in banning assault rifles — in the U.S., at least, handguns are responsible for most gun deaths – but in facing and acting decisively and credibly against the reality that hatred and the violence it can spawn knows no boundaries.

The world should be a place where people can say, even to a stranger, “Hello, brother,” without getting a bullet in return.