Books and covers

Not every Muslim is a terrorist.
This one, Salman Taseer (far right in the picture) is a martyr:

A police official takes the thumb print of Aasia Bibi, a Pakistani Christian woman who has been sentenced to death for blasphemy, on an affidavit stating her innocence after she was visited by the Governor of the Punjab Province Salman Taseer (R) at the central jail in Sheikhupura, Punjab Province, on November 20, 2010.

The Punjab governor, Salman Taseer was shot by own bodyguard, who opposed reform of Pakistan's blasphemy laws. It is dangerous to be a moderate in the Muslim World.

Not all Christians are saints. This Christian was a terrorist:

Hitler wth Archbishop Cesare Orsenigo, the papal nuncio in Berlin, 1935
On April 20, 1939, Archbishop Orsenigo celebrated Hitler's birthday. The celebrations, initiated by Pacelli (Pope Pius XII) became a tradition. Each April 20, Cardinal Bertram of Berlin was to send "warmest congratulations to the Fuhrer in the name of the bishops and the dioceses in Germany" and added with "fervent prayers which the Catholics of Germany are sending to heaven on their altars."

Atheists are not without guilt. This atheist freed the people from the opiate of religion but he was a terrorist:

Under the dictatorship of Joseph Stalin, tens of millions of ordinary individuals were executed or imprisoned in labour camps that were little more than death camps. Perceived political orientation was the key variable in these mass atrocities. But gender played an important role, and in many respects the Purge period of Soviet history can be considered the worst gendercide of the twentieth century.

It's not the religion or the lack of it, it's not the gun or the lack of it - the problem is older and deeper than that.