Diana West's splendid new book, "American Betrayal: The Secret Assault on Our Nation's Character," is an expose of a practice that she persuasively argues has cost us dearly in the past and endangers our future. Former federal prosecutor-turned-pundit Andrew C. McCarthy calls it "willful blindness," and we indulge in it at our extreme peril.

Ms. West painstakingly documents how America's government, media, academia, political and policy elites actively helped obscure the true nature of the Soviet Union. She persuasively argues that such blinding began literally from the moment in November 1933 when Franklin Roosevelt normalized relations with the USSR in exchange for the Kremlin's fraudulent promise to forgo subversion against this country.

Ms. West came to this exhaustive research project by dint of her curiosity about the failure of such elites in our own time to recognize and counter today's present danger: the Islamists and their Shariah doctrine, which some have described as "communism with a god." Several examples illustrate willful blindness in our time:

Army Maj. Nidal Malik Hasan, whose trial for the Fort Hood massacre finally begins this week, repeatedly signaled his intention to engage in such an act of jihad prior to gunning down his comrades. Testimony is expected to show that officers in his chain of command refused to entertain such a possibility - and actually threatened the careers of those who had the temerity to warn of the violent mayhem this Islamist believed he must inflict, pursuant to Shariah.

Such dereliction of duty was compounded by a serious error by the nation's first line of defense against such internal threats - the FBI. Thanks to communications intercepts by the lately much-maligned National Security Agency, the FBI was aware that Maj. Hasan was being mentored about his duty under Shariah by an al Qaeda-associated cleric then based in Yemen, Anwar al-Awlaki. Yet, rather than move in on Maj. Hasan, the FBI dismissed such counseling as nothing more than research for the major's thesis at a U.S. military medical school.

The FBI's performance against such jihadists has been further hampered by the influence operations of Muslim Brotherhood-linked individuals and organizations who are now "inside the wire" of the U.S. government - in a manner all too reminiscent of the penetration of our governing and other institutions by Soviet agents during the 20th century, chronicled so brilliantly by Ms. West. The training materials of not only the FBI, but the military, the intelligence community and homeland security agencies, have been purged of information that would help connect the dots between the supremacist Islamic doctrine of Shariah and terrorism.

Such self-imposed blinding about the enemy's threat doctrine is dressed up as multicultural sensitivity and political correctness, aimed at not gratuitously giving offense to Muslims. In fact, it amounts to submission to our enemy's bid for what the U.S. military calls "information dominance." There seems little doubt that these sorts of imperatives contributed to the FBI's inability, despite some 14 hours of interviews with Tamerlan Tsarnaev, to discern the jihadist proclivities of a man who subsequently acted on them to perpetrate the Boston Marathon attack in April.

Meanwhile, the Obama administration has throughout its tenure submissively aided the Muslim Brotherhood in Egypt, by legitimating, empowering, funding and even arming it. While this public embrace has diminished somewhat since the Egyptian military responded affirmatively to popular demands for the overthrow of the Muslim Brotherhood regime of Mohammed Morsi, Team Obama insists that the avowedly anti-democratic organization nonetheless be allowed to participate in any future electoral process.

This has required a determined effort to ignore the true agenda of the Muslim Brotherhood, both there and here. Particularly alarming are the findings of a detailed analysis by counterterrorism expert Patrick Poole, recently documented in the Middle East Review of International Affairs. Mr. Poole documents how, time and again, one element of the U.S. government, under both this and previous presidents, "reached out" to Muslim Brotherhood figures and organizations, even as they or their associates were being investigated by other agencies for material support for designated terrorist groups, subversion or preparations for jihadist attacks.

A particularly glaring example of willful blindness involves the almost complete suppression of information about Huma Abedin's extensive Muslim Brotherhood ties. Despite the incessant coverage of Anthony D. Weiner's wife on many other scores, there has, for example, been scarcely any discussion of her role as the State Department's deputy chief of staff in the Benghazigate scandal. Hopefully, the report last week by CNN that 35 witnesses to the jihadist attack on the CIA annex are being actively suppressed, intimidated and pressured not to tell the Congress or the American people what happened on Sept. 11, 2012, will lead to a proper investigation. It must illuminate, among other things, the Abedin connection and Hillary Rodham Clinton's serious misjudgment in giving a woman with such associations a succession of positions of trust over the past 16 years.

Neither the American people nor those they entrust with their security can afford to engage in delusional fantasies about the enemies we face at home as well as abroad.