While not all terrorists are Muslim (some are Communists, some are evironmentalists), the fact remains that most acts of violent terrorism in the world on a daily basis are committed by Muslims.
And these acts are committed by Muslims to either scare others into converting to Islam in the hopes that they aren't killed later or into submitting to Islam's theocratic rules (Shariah law) that privileges Islam in a way that gives you a hundred daily reasons to convert. In this regard, Islam is both a religion and a political system. The moderates say you can be Muslim while ignoring the holy book's demands to create a Muslim dominant government that enforces the religious rules on EVERYONE, while the fundamentalists demand that the political Islam be implemented. This is why you see Shariah patrols in the EU trying to punish all women not covered up, beating people for drinking alcohol, etc.
And all these acts are according to the Koran. Mohammed repeatedly said in the Koran fight until all the world believes in Islam, fight until all submit to Shariah law, cut off their fingers to scare them into converting, that it is better to die than be an unbeliever.
Mohammed personally led raids to kill all people in a village that didn't convert to Islam. Obviously he supported the murder of those who don't convert to Islam when offered - he provided an example of that, and Muslims consider him the perfect example.
He praised a follower for killing a female poet who mocked him. A separate poet was killed for mocking him. Thus the Koran clearly states in both verse and historical examples of killing critics ... this is why over a quarter of Muslims in the West support jail or death sentences for critics of Islam. Freedom dies when we accommodate a religion contrary to free speech.
Making things worse is the more recent influx of immigrants from the poorer, more conservative Muslim regions. Over half of YOUNG Muslims say yes, Shariah law should dominate the West, no matter what the local people say. A quarter support violence to impose Shariah law, with between a third and a quarter (depending on the nation) saying no, they won't turn in a family member planning terrorist acts.
When a sizable minority of the young adults in a religion IN THE WEST say yes, they get to impose their faith on everyone else and endorse violence to do so, we can say the problem is the violent ideology, Islam.