Radical Islam threatens American democracy. It is slowly subverting America from within and without. If it is not stopped, U.S. civilization is doomed.

For decades, Europe has been in the grip of an Islamist assault. Largely ghettoized Muslim populations have become dangerously alienated from the European mainstream. From Paris to Hamburg, Germany, radicalized imams preach the virtues of global jihad. Subway systems in London and Madrid have been bombed; hundreds of civilians have been slaughtered. Dutch filmmaker Theo van Gogh was murdered.

These atrocities were committed largely by homegrown terrorists — people who were either born or raised in European countries. They felt no loyalty to their homelands. Instead, they considered themselves part of the Muslim ummah, the international Islamic political community. Their religious identity supersedes their national one.

America faces the same kind of threat. Yet when anyone tries to put a spotlight on the growth of domestic Muslim extremism, liberals, Islamic lobby groups and their fellow travelers cry “Islamophobia” and “racism.”

The latest example was the congressional hearing held by Rep. Peter King, New York Republican, who dared to examine how some U.S. Muslim youth are being radicalized and recruited by terror networks. The American Civil Liberties Union, the Council on American Islamic Relations (CAIR) and the Democratic Party all claimed the hearing was not only unjustified and deeply discriminatory, but could spark an intense backlash among many in the U.S. Muslim community. The critics even argued that this could provide fodder for Al Qaida and other jihadists to commit more terrorist acts. In other words, Islam is a “religion of peace” unless you investigate some Islamic extremists who may be plotting to kill or maim Americans; then that will compel peaceful, law-abiding Muslims to wage jihad. This is the twisted — and perverse — logic of the multicultural left.

The overwhelming majority of Muslims — both in and outside America — are decent, nonviolent individuals. They want what most people want: to raise their families in dignity without being harassed. Yet there is a significant minority — many experts claim it is between 7 percent and 10 percent of the population — who are radicalized. They seek to erect a global caliphate based on Shariah law. Their goal is to destroy the West. There are more than 1 billion Muslims in the world. Simple math suggests there is a potential army of jihadists out there.

U.S.-born militant Muslims have been waging an internal holy war — one that has received little to no attention in the mainstream media. Take Army Maj. Nidal Malik Hasan. Maj. Hasan is accused of committing in November 2009 the most devastating terrorist atrocity on U.S. soil since the Sept. 11, 2001, attacks. He is charged with deliberately gunning down 13 colleagues and wounding 30 others at Fort Hood, Texas, explicitly in the name of political Islam. The difference between Maj. Hasan and the Sept. 11 hijackers is his citizenship: He was born in America of Palestinian Muslim parents.

Maj. Hasan has not been the only one. In June 2009, a 23-year-old Army recruiter in Little Rock, Ark., was killed by a black American convert to Islam. The killer admitted that his motivation was opposition to the war in Iraq. Five Muslim men — born and raised in and near Washington, D.C. — were arrested in Pakistan for trying to wage guerrilla war against U.S. forces in Afghanistan. The list goes on. Yet liberals refuse to acknowledge the obvious: We are in an ideological struggle with Islamic fascism.

The price for speaking out against creeping Islamism is very high. Just ask talk-radio host Michael Savage. The populist conservative is one of the most listened to and influential voices in the media landscape. Mr. Savage is a rare breed: a nationalist who opposes the socialist New World Order. He is a vocal critic of Western society’s gradual surrender to political correctness and growing Islamic extremism.

CAIR has been seeking to muzzle him for years. His criticisms of Shariah law and Islamist barbarism have landed him in hot water. Under the previous Labor government, Britain banned Mr. Savage from entering the country. He has been put on a blacklist alongside Hamas killers, murderous Russian skinheads and neo-Nazis. He has never advocated or committed violence. In fact, he is a champion of democracy and human freedom. Prime Minister David Cameron has refused to lift the ban. The goal is clear: Mr. Savage is to be sacrificed on the altar of multiculturalism.

The ban is a fundamental assault on freedom of speech. Mr. Savage has been living with a huge target on his back; the ban tacitly encourages jihadists to assassinate him. It whets the limitless appetite of Muslim fanatics everywhere. Today, it is Mr. Savage; tomorrow, it could be any other prominent spokesman on the right. The ban is a cultural watershed — a key battle in radical Islam’s relentless advance. Instead of defending him, most Republicans have turned their backs.

One of the few exceptions is Rep. Allen B. West of Florida. Mr. West recently wrote a letter to Secretary of State Hillary Rodham Clinton asking that the State Department look into the ban and demand that Britain overturn it. It won’t happen. Foggy Bottom is not interested in defending democratic values or free speech — never mind the innocence of an American citizen who has spent his career speaking truth to power.

That truth — especially that Islamic fundamentalism poses a mortal threat to the West — is precisely what Mrs. Clinton and the ruling class do not want to hear. They are too busy worshipping the false god of multiculturalism.