The campaign to hand out the Korans drew nationwide attention — and widespread condemnation — last week after journalists who had criticized the effort were threatened in an online video. And on Monday, the interior minister in Hesse, a state in central Germany, called Mr. Abou-Nagie and his followers “pied pipers” and said that the danger from radical Islam had reached “a new dimension.”

But Rauf Ceylan, a professor of religious sociology at the University of Osnabrück, said that violent extremists represented “a minority within a minority” and that the discussion of Muslims’ participation in German society should not be focused on Salafists. “Politicians have a great responsibility for communicating the fact that Germany is now an immigration society,” he said, “and thus far they have failed at that.”

The role of Islam in Europe has been fiercely contested in the decade since the attacks of Sept. 11, 2001. Moderate Muslims say that officials’ emphasis on extremist groups and terrorism helps contribute to a climate of fear that can lead to violence, like the killings last summer by Anders Behring Breivik in Norway.

A German security official who did not want to be quoted by name because of the delicacy of the issue said officials were worried that disaffected, directionless young people would be drawn to what he called the Salafists’ simplistic interpretation of the Koran and find inspiration in it for violent acts.

He cited Arid Uka, who opened fire at a bus carrying American airmen at a Frankfurt airport in March 2011, killing two and wounding two others. Mr. Uka, who was born in Kosovo but had lived in Germany since he was a child, said he had become radicalized by reading Web sites, including some linked to Salafist groups in Germany.