1. The greatest good in Islam is spreading the idea of Islam. Because of that, atrocities that scare people into converting to Islam to avoid a similar faith ARE permissible in Islam. There are examples of this in the Koran. Kill a few people in a gruesome way and advertise it, warn others that if they convert it won't happen to them, many convert, the killings are therefore moral because it brought more people to the religion. That is the reason for terrorist violence and why it is moral in Islam. So is lying to protect the faith (taqqiya).
2. Most terrorist acts on the planet are committed by Muslims, either against non-Muslims or other Muslim sects (Shia versus Sunni, Shia and Sunni against Sufi and Almadi). The fact that most Muslims don't commit violence doesn't mean that Islam isn't what is driving it.
Wafa Sultan - the peaceful majority is irrelevant.
3. Islam supports violence to enforce social control. This is why 90% of all honor killings are Muslims against their own female relatives. It is also why you have Muslim mobs in Pakistan killing atheists, why Malala Yousef was shot by the Taliban
4. Islam doesn't mean peace - it means submission. That means everyone follows Islamic rules, even if they aren't Muslim. Indonesia just caned a Christian woman for selling alcohol during Ramadan. Saudi Arabia and Iran do the same thing all the time. A religion that says we won't hurt you if you follow our rules is compulsion to the religious rules even if not compulsion of religion.
5. There is a logical fallacy called the no true scotsman fallacy. The man is seen as a true Scotsman until he is noted as doing something controversial, and then everyone says he's not a real scotsman.
From the Orlando Pulse shooter to ISIS, they commit acts per the Koran, mimicking Mohammed's example, with support of various clerics, and Muslims scream "not all Muslims!" When thousands of incidents a year are committed by Muslims in the name of Islam per the example of the religion's founder and the holy book, it IS Islam ... and the fact that Muslims say "they are not really members of the tribe" instead of "that's not how to interpret the text" is an admission it IS Islam. If the interpretation was that wrong, the murderers would be denounced. Instead, they are distanced while no one says they were really evil.