Los Angeles County Sheriff Lee Baca, considered an expert on fighting terrorism, cautioned the committee not to single out the Muslim American community as more prone to radicalization, saying it gives a false impression.
However, New York Rep. Peter King, the committee chair, said homegrown radicalization is part of al Qaeda's strategy to continue attacking the United States.
King has accused the American Muslim community of not doing enough to speak out against terrorism or help police.
Baca countered that Muslim Americans have helped foil seven of the last 10 plots propagated by al Qaeda within the United States. He also said the sheriff's department works hard at building trust with Muslim Americans.
"It is counterproductive to build trust when individuals or groups claim that Islam supports terrorism," Baca testified. "This plays directly into the terrorist propaganda that the West war on terror is actually a war against Islam."
Baca said police must have the trust and understanding of all communities.
"The Muslim community is no less or no more important that others because nobody can predict with complete accuracy who or what will be the next threat to our nation," Baca said.
The Obama administration has also expressed worries about broad statements about an entire religion.
"To back down would be a craven surrender to political correctness and an abdication from a terrorist attack," King said.
Congressman Keith Ellison, a Muslim, said the hearings could backfire.
"Ascribing evil acts of a few individuals to an entire community is wrong," Ellison said. "It is ineffective and risks making our country less safe."
Muslim leaders have said the inquiry is overbroad and paints all Muslims as terrorists or potential terrorists.
Salam al-Marayati of the Los Angeles Muslim Public Affairs council said he's s especially critical of King's statements about al Qaeda and Muslim Americans.
"That is a little of McCarthyism when he talks about al Qaeda's affiliates in the United States," Al-Marayati said. "He can't really point to someone representing al Qaeda among the Muslim American organizations."
The top Democrat on the committee, Bennie Thompson of Mississippi, says he believes the hearings could be used to inspire terrorists.
"I cannot help but wonder how propaganda about this hearing's focus on the American Muslim community will be used by those who seek to inspire a new generation of suicide bombers," Thompson said.
Critics have likened the hearings to the McCarthy-era hearings investigating communism.