The intolerance advocated by some groups has been exacerbated by occasional calls for violence, as well as incidents of violence. For example, on February 4, 2011, a Muslim man was stabbed in the neck with a pocket knife at a bar in St. Petersburg, Florida. During a verbal altercation preceding the incident, the attacker allegedly told the victim, "Muslims are the root of the problems," according to the arrest report. In August 2010, a man stabbed a New York City taxi driver in an apparent hate crime. The attacker allegedly asked the driver if he was Muslim, referenced military checkpoints and uttered an Arabic phrase before attacking the taxi driver with a knife.

The actions of a Norwegian terrorist, who murdered dozens of children at a summer camp and set off a bomb that killed others in the government district in Oslo, were apparently influenced, in part, by anti-Muslim voices in the U.S. This tragic incident serves as reminder of the influence these hateful ideologies pose.

The suspect in the July 22, 2011, attacks, Andrew Behring Breivik, published a 1,500-page manifesto quoting from the writings of European and American anti-Muslim writers, including Robert Spencer and Pamela Geller of Stop Islamization of America (SIOA), who promote a conspiratorial anti-Muslim agenda under the pretext of fighting radical Islam.