The Muslim community in America is not a monolith. Very broadly, it comprises three groups: African-Americans (many of them converts), immigrants (largely from the Middle East and South Asia) and white converts. And Muslims from every part of the world study and work in the United States.

Yet the diversity of the Muslim community is frequently obscured by ignorance and mistrust. We were often asked by non-Muslims whether Muslims could be “good” Americans. The frequency with which this question was asked indicated the doubts that many harbored. Too many Americans acknowledged that they knew virtually nothing about Islam and said they had never met a Muslim.

Representative King, the New York Republican who has called the hearings, has raised the issue of Muslim cooperation with law enforcement agencies. On our journey, especially in mosques, we confronted an underlying unease and suspicion toward these agencies. Frequently, even while we were being welcomed and honored, people would ask us with a nervous laugh whether we were working for the F.B.I. The community complained that crude attempts by the agencies to “study” them were both insulting and ineffective. They believed that thinly disguised informants who claimed to be converting to Islam were acting as provocateurs.

In a Texas mosque dominated by the Salafi school of thought  widely equated with religious fundamentalism  the congregants condemned terrorism. They complained that the agencies had used clumsy infiltrators instead of simply talking to congregants. “Homeland Security and F.B.I. put us under surveillance, asking people, ‘Where are the terrorists?’” one interviewee, a Salafi who professed nonviolence, told us. “We know exactly where they are!”

At times, we did see evidence of the kind of extremist beliefs the hearing is intended to scrutinize. In one of the first mosques we visited in the Midwest, after I gave a talk advocating interfaith dialogue, I was accosted by members of the congregation who vehemently disagreed and dismissed my fieldwork because I had “white kids” with me. Later we learned that these men had threatened and assaulted other congregants who did not agree with them.

In our review of cases involving radicalized American Muslims, we learned that many homegrown terrorists said their actions were grounded in American foreign policy, particularly when it resulted in the deaths of women and children, rather than in their interpretations of Koranic precepts. In public statements, they expressed anger about American military and intelligence intervention in Iraq, Afghanistan and other Muslim countries. For example, Faisal Shahzad, the Pakistani immigrant who confessed to the attempted car bombing in Times Square last May, was motivated by a desire to avenge drone strikes in his native province.

If a civil, respectful level of discussion and debate is not maintained in these hearings, and if a demonization of Muslims results, the news coverage in the Muslim world could feed into the high levels of anti-Americanism in countries like Afghanistan and Pakistan. This would play against the interests of American diplomats and troops in Muslim nations who have advocated the winning of Muslim hearts and minds.