The Israel branch of the Anti-Defamation League on Sunday sent a letter to Attorney General Avichai Mandelblit calling on him to act against the head of a radical right-wing organization named in a recent report as a top inciter of online racism against the Arab population and minority groups.

The ADL said in the missive that it was following with concern “the extremist and litigious dialogue in Israeli society and in particular the radical dialogue” led by Bentzi Gopstein, the chairman of the Lehava anti-assimilation group.

A report from the Israel Religious Action Center published earlier this month, which looked at violent and offensive online comments against the Arab population and other minorities in Israel, highlighted the activities of Gopstein and Lehava.

“Gopstein and the organization that he heads are leading a radical line that has destructive consequences for Israeli society,” the ADL wrote. “Gopstein’s Facebook page is full of hateful content and remarks, in no uncertain terms, in the main part against the Arab population. The opinions expressed on it, by him and his followers, are offensive, racist, inciting and very violent.”

The ADL said it urged Mandelblit to use all means at his disposal to “lay down a clear red line against a phenomenon that poses a danger to democracy and society.”

“We believe it is our duty to defeat this hateful dialogue, which has already led to ‘price tag’ crimes,” the ADL noted, referring to acts of arson and vandalism carried out by right-wing Jewish extremists that target Arab and Christian property.

In November 2014, three Lehava members set fire to a Jerusalem school that teaches Muslims, Christians and Jews. The group also regularly holds demonstrations in flashpoint areas of the capital’s Old City and in other parts of Israel with a large Arab population, and its members have been known to physically assault Arabs.

The ADL pointed out that beyond the damage that racism causes to Israel internally it also tarnishes the Jewish state’s appearance abroad.

“From our point of view, as an organization which is headquartered in the US, we see that this hateful dialogue doesn’t just harm Israeli society, but also Israel’s image. The dialogue…along with its damage to Israeli society, is used as a weapon by Israel’s enemies who are quick to draw from it conclusions about all of Israeli society.”

In a response from Gopstein reported by the Israel National News website, the Lehava head rejected the accusation that his Facebook page was problematic.

“I call on the ADL that they are the ones who should first of all check what is going on with the Israel-hating Arabs on Facebook,” he said. “Every few seconds there is another post and another post that calls for the murder of Jews. They shouldn’t be busy with good Jews.”

He insisted that material uploaded to his Facebook page — much of which urges Jewish women to not fraternize with non-Jewish men, and Arabs in particular — is all legal and “out of concern for the daughters of Israel.”

He added: “Thank God they [the ADL] are against me, that way I know I am on the right path.”

Carol Nuriel, the director of ADL’s Israel office, recalled some of Gopstein’s recent comments in a statement Tuesday, including “the use of racist and offensive expressions against the Christian religion, which he called a ‘cursed religion’ and its believers ‘blood-sucking vampires,’ as well as a call for the Israeli Reform Judaism movement ‘to be dammed.'”

“Words lead to actions and the stated matters raise great concern,” Nuriel said. “We need to stop this incitement, and the sooner the better. Racism and incitement harm the groups they are targeting and the society in which they exist and we all have a responsibility to act against them.”

Gopstein has been arrested and detained by police several times in recent years, but has never been convicted of incitement or other criminal activity related to his controversial group.

Lehava has frequently called for action to be taken against non-Jews and homosexuals in order to “save the daughters of Israel,” in Gopstein’s words.

In April, the Jerusalem Magistrate’s Court acquitted Gopstein of assaulting two left-wing activists he mistook for Palestinians sneaking into Givat Avot, a Jewish neighborhood in Hebron, where he was living almost a decade ago.

Last year Gopstein wrote an article titled “To overthrow the vampires,” in which he called Christians living in Israel “blood-suckers,” and has publicly called for the burning of churches.

Tamar Pileggi contributed to this report.