A Nov. 17 meeting on the possible new location of the Islamic Center of Fredericksburg was interrupted by anti-Muslim protesters. (PETER CIHELKA/The Free Lance-Star)

AT THE front of the room, a representative of the Islamic Center of Fredericksburg, which seeks to build a larger facility than the one it has inhabited peaceably for 15 years, was talking the lingo of planning and permitting. The protesters who kept interrupting him spoke a different tongue: the language of hatred.

“Nobody, nobody, nobody wants your evil cult in this county,” one man said as he jabbed his finger at Samer Shalaby, a Muslim trustee of the center. “I will do everything in my power to make sure that that doesn’t happen, because you are terrorists. Every one of you are terrorists. . . . Every Muslim is a terrorist.”

An astonished Mr. Shalaby responded evenly, “How did you come up with that?”

After a few more minutes in that vein, a nervous sheriff’s deputy, having appealed in vain for civil discourse, stopped the meeting and told everyone to go home.

Bigotry has a long history in the United States, and it may come as only a mild surprise that it showed its snarling face in Fredericksburg last week, just four days after the Nov. 13 slaughter in Paris. But even mild surprise is unwarranted given the toxic rhetoric of presidential candidates and governors, mainly Republicans, who have vilified Muslims since that terrorist attack.

When Donald Trump, Ben Carson and others suggest it is all right to discriminate against Muslims or Muslim refugees, the signal is widely received. On a small scale, the reception given the proposal to build a bigger mosque in Fredericksburg is an example. Many or most of the 150 or so people at the meeting seemed more tolerant and open-minded. But the loudmouths who vented their poisonous views dominated the proceeding, and no one had the appetite to take them on.

To the community’s credit, the Islamic Center has since been deluged by gestures of support from well-wishers, as well as from some elected officials in an area that’s heavily Republican. Rep. Dave Brat (R), who represents the district in Congress, told us he was “appalled to learn about what happened to these long-time, peaceful Islamic residents . . . and I condemn the threats against them.”

Yet Mr. Brat also supports a GOP-sponsored bill that would make it more difficult to admit Syrian refugees into this country. That bill, though it has little chance of becoming law, contributes to the mood of intolerance.

Lured by affordable housing and available jobs, hundreds of Muslims in recent years have settled in the Fredericksburg area, about 50 miles south of the District. They are a peaceable community. The Islamic Center, a modest brick building with inadequate parking on a dirt lot, needs more space. Three years ago it purchased a 10-acre parcel nearby, with an eye toward building a bigger mosque with more parking.

The nation will now watch how local officials in Spotsylvania County, which adjoins Fredericksburg, handle the center’s request. The decision should be based on the merits of Mr. Shalaby’s arguments on parking and zoning, not on the bigotry and intolerance that national leaders are cynically bringing into the mainstream.