The result: Roberts lost "a bunch of church members," he said.
And at Hillsboro Presbyterian Church in Nashville, Tenn., Nancy McCurley started an interfaith Scripture study with local Muslims, only to be told by a critic that "in a year's time, this church will be a mosque."
In the 10 years since the 9/11 terrorist attacks exposed the deep divide between America's Judeo-Christian majority and American Muslims, a host of projects have tried to foster interfaith understanding.
To be sure, there have been signs of hope for the future of interfaith relations. But along with progress has come polarization—threats of Quran burnings, protests of proposed mosques and fears of Islamic law in the U.S. legal system.
A month after the 9/11 attacks, an ABC News/Washington Post poll found that 47 percent of Americans had a favorable opinion of Islam. By 2010, that figure had only gotten worse, dropping to 37 percent.
That begs the question: Has the flurry of activities aimed at interfaith understanding actually accomplished anything?
Eboo Patel, founder of the Chicago-based Interfaith Youth Core, said the furor over the proposed Park51 Islamic cultural center near Ground Zero highlighted the need to gauge the quality, not just quantity, of interfaith efforts.
"Tens of thousands of people in the country who were participating in interfaith projects basically were watching this on TV, ... saying, 'What difference does our work make on a national level?'" said Patel, who is Muslim.
As activists like Patel push to foster meaningful relationships between Islam and other faiths, there has been pushback from groups who have no interest in such relations, or who question aspects of Islam.
Gustav Niebuhr, author of Beyond Tolerance, said the divide reflects three types of Americans—the pro-interfaith crowd, the anti-Muslim segment and "the-don't-know-too-much middle" that can be swayed by either side.
Recently, the two poles have debated the possible influence of Shariah, or Islamic law, even though there has been no concerted effort by American Muslims to introduce it into American courtrooms.
"The problem is when people think of Shariah, the only image that comes to mind is the Taliban stoning some poor woman to death in Afghanistan," said Niebuhr, a professor at Syracuse University. "That's the outer limit."
In a growing circle of evangelical churches, there has been a sort of reverse pushback by leaders who are turned off by fellow Christians trying to block mosque construction and blaming Islam for 9/11.
Joseph Cumming, an evangelical who directs the Yale Center for Faith and Culture Reconciliation Program, said more evangelicals are asking what Jesus would do when it comes to relating to Muslims.
"There's a hunger in churches to ask that question," he said. "That wasn't being asked before 9/11."
Mahan Mirza, vice president of academic affairs at Zaytuna College, a new Muslim school in Berkeley, Calif., said Christian-Muslim relations generally are better on the local level, where he has seen an increase among evangelicals who think the Bible requires such outreach.
"Sometimes that's couched in the language of love your enemy so ... it's not done in spite of Christian teachings; it's done because of Christian teachings," said Mirza, a former professor at the University of Notre Dame.
Last year, Rick Love started Peace Catalyst International in Chandler, Ariz., which sponsored dinners with members of a local mosque and his Vineyard church to foster what he calls "Jesus-centered peacemaking communities."
He cautions fellow evangelicals to be humble before criticizing the harsh punishments demanded by others' scriptures: "I praise God that we don't live under the Old Testament," he said.
Yet some evangelical leaders, including Southern Baptist agency executive Richard Land, have been condemned for supporting Muslims.
"Southern Baptists were comfortable with me advocating that Muslims have the right to have mosques," said Land, who supported a proposed mosque in Murfreesboro, Tenn. "What they were not comfortable with was me being part of a coalition that was filing a suit in order for them to have these mosques."
Suhail Khan, a Muslim member of the advisory council of the interfaith Buxton Initiative, said he is alarmed Americans' declining favorable views of Muslims.
He blames a "cottage industry of hate" for the shift and finds himself answering more questions about Shariah than the basics of what Muslims believe when he visits evangelical churches.
"I'm having to undo all kinds of misinformation and very hateful misinformation," said Khan.
Undeterred, Patel puts much of his hope in the 200 colleges and seminaries—including nine evangelical schools—that participated in a recent White House event kicking off yearlong interfaith service projects. He expects many of the students will eventually launch similar projects at companies and in cities where they move after graduation.
"I think that college campuses are going to be models of interfaith cooperation, and I think they're going to graduate a generation of interfaith leaders," he predicted.