The specter of the late commie-hunting congressman from Wisconsin, Joseph McCarthy, will always be with us. It was summoned up recently to describe Rep. Michele Bachmann, R-Minn. She and four other Republican members of Congress wrote the State Department inspector general to investigate a longtime senior aide to Secretary of State Hillary Clinton. The aide's family, her letter pointed out, has ties to the Muslim Brotherhood.

The response to these charges was mostly outrage. Sen. John McCain defended the aide as "a dedicated American." There is no evidence that he is incorrect. Yet, the larger and more important issue is being obscured here. Many in government and the media don't even want to face the possibility that infiltration is a tactic of Islamic extremists who repeatedly say they want to destroy not only Israel but the "Great Satan" America. Such objectives should be taken seriously, given their violent history.

One need not rely on the word of Bachmann -- try instead that of former British Prime Minister Tony Blair. Charles Moore of the London Daily Telegraph writes that Blair "now thinks, he underestimated the power of the bad 'narrative' of Islamist extremists. That narrative -- that 'The West oppresses Islam' -- 'is still there. If anything, it has grown.' It seeks 'supremacy, not coexistence.' " Blair also expressed fear that "The West is asleep on this issue."

Blair's view is echoed in "Battle for Our Minds: Western Elites and the Terror Threat," a new book by Michael Widlanski, a specialist in Arab politics and a former journalist for mainstream publications such as the New York Times, the Cox Newspapers' Atlanta Journal-Constitution and the Jerusalem Post. Widlanski's main point is that political correctness has stifled the West's ability to understand and fight terror.

Among Widlanski's criticisms is that the West "came to rely on 'experts' without field experience in or scant knowledge of the Middle East: people who do not speak the languages, did not study the cultures and do not know the history. Even worse, some 'experts' have been forgiving and even sympathetic to the terrorists and their aims."

National Public Radio reported last month that "The FBI has conducted more than 100 investigations into suspected Islamic extremists within the military."

What else would infiltration look like? It's more than an academic question, or a subject for spy novelists. It might look like CAIR, the Council on American-Islamic Relations, which sent a nasty letter to Bachmann comparing her to McCarthy. Documents released from the 2007 Holy Land Foundation trial in Dallas, in which the feds prosecuted extremists for funding Hamas and other "Islamic terrorist organizations," revealed that the founders and current leadership of CAIR were part of the Palestine Committee of the Muslim Brotherhood.

In 2009, federal Judge Jorge Solis denied CAIR's attempt to have its name struck from all of the Holy Land trial's documents -- the group had been named as an unindicted co-conspirator. "The government," Judge Solis noted, "has produced ample evidence to establish the associations of CAIR, [the Islamic Society of North America] and [the North American Islamic Trust] with [the Holy Land Foundation], the Islamic Association for Palestine, and with Hamas."

According to the Global Muslim Brotherhood Daily Report, which covers the brotherhood, the deputy leader of the Egyptian Muslim Brotherhood recently gave an interview confirming a relationship between his organization and CAIR.

This is what infiltration looks like. It is real, and Bachmann's involvement does not change the fact that it is real. All ties between Americans and Islamic extremist groups need further and serious investigation.

Examiner Columnist Cal Thomas is nationally syndicated by Tribune Media.