Just as terrorism in the name of other religions has existed throughout history. We must call evil things by their name if we want to overcome them.
Pope Francis declared in February that there was no such thing as Islamic terrorism. By doing so, he negated the existence of terrorism that is inherently religious in nature whether it's Christian, Jewish or Muslim. I do not dispute his good intentions — he avoids slandering a whole religion because some of its followers commit acts of terror — but I do have a serious problem with the actual truth of his assertion.
History provides us with many examples of religious terrorists. The Jewish assassins who cut the throats of Romans and their own compatriots in a war against Rome (66-73 AD) invoked the God of Israel. Jesuits did the same to non-Catholics even if it does seem ironic to do so considering the teachings of Jesus Christ. The Islamic case is essentially different, as I point out in my book Mahoma, el guía ("Muhammad the Guide").
Prophet Muhammad was a different character before and after the year 622. Prior to that year, he was a peaceful man who announced the approach of the Day of Judgment, and urged people to submit to The One God.
In 622, when Muhammad left Mecca for Medina, he became a military ruler who used the sword to spread his word. Since Islam considers Muhammad's life a model for emulation, even in its smallest details, this change of path would lay the foundation for legitimizing various forms of violence including terrorism.
While there are Muslim terrorists whose actions cannot be attributed to Islam. Many Muslims are, certainly, opposed to terrorism. But this does not mean that Islamic terrorism is not, as the pope claims, simply terrorism perpetrated by Muslims. ISIS, al-Nusra, Hamas, Hezbollah and similar groups backed by regimes in Saudi Arabia, Sudan and Iran, are terror groups that invoke Islam in their actions.
This makes Islamic terrorism a real threat, even though many leaders, including the pope, are regrettably unable to face that fact.