In recent decades, Muslims have obviously been the overwhelmingly dominant perpetrators of religiously-motivated extremist violence, targeting non-Muslims and their allies within the Muslim community, as well as Muslim sects which they consider deviant from orthodox Islam. But over the last couple of decades, extremist violence by non-Muslims, targeting people of differing faiths, has been becoming increasingly frequent. And disturbingly, an Islamic connection is becoming a common motivator of these non-Muslim extremist violence: Non-Muslims commit those violence due to instigation by Muslims or as retaliation to preceding violence by Muslims.
In the West, the last time a non-Muslim extremist committed a major terrorist massacre was the Oklahoma City Bombing by Timothy McVeigh (professed to be an atheist of Christian heritage) on April 19, 1995 that killed 168 people and injured 450. McVeigh's motive was his anger at the Waco Siege at Texas (February 28 to April 19, 1993) by the FBI that left 76 people of the infamous David Koresh-led Davidian Sect dead.
And whenever extremist Muslim groups or individuals have committed similar terrorist atrocities in recent years, we have been reminded by Muslims and their apologists with reference to the McVeigh incident that people of all persuasions -- Islam, Christianity, Judaism, White Supremacism, Communism, and such -- can commit extremist violence. So, Islam should not associated with extremism and terrorism for the actions of its individual followers, just as violence by a Christian or Jewish extremist must not be attributed to their faiths.