1. Thousands of Muslim fundamentalist attacks around the world each year, a far higher rate than any other faith - and the violence IS per the Koran. Many verses calling for death of the infidel, death of those who will not convert to Islam, death to apostates and atheists and homosexuals.
2. 90% of all honor killings are by Muslims, when they are only 30% of the world population. A faith whose members are three times more likely to kill wives and daughters is not a good one.
3. Islam is violent as detailed in the Koran from the moment in Medina Mohammed was rejected by the Jews and called for their deaths if they didn't convert, as well as a hatred of everyone else who was not Muslim or subordinate to Muslims paying the dhimmi taxes and second class status. So all the violent acts from ISIS to Boko Haram to Urgyur terrorists in China are per the Koran and Mohammed's example. No other major religion was spread mostly by violence, and NO religion except Islam retains the supposed right to conquer the world.
4. Many Muslims actively deny the violent portions of the Koran, though it is the majority of the book. And they deny the violent fundamentalists praising Allah, quoting the Koran and acting per the religion's founder's example are Muslim. This is a "no true Scotsman" logical fallacy, a convenient way to excuse it. This is is actually immoral, because it denies the part of the religion that needs to be reformed and contextualized (to say the violent verses were for then and there, not here and now).
5. A large majority of Muslims according to Pew Polls agree with the most violent parts of the Koran like killing apostates (those born Muslim who convert to another faith), killing atheists, killing someone who commits adultery. And more than half of young Muslims n the West say they want Sharia law that mandates the murders I listed above as the law of their new homes. When the majority of a population supports overthrowing liberal secular government and ending human rights because its religion says so, that is a threat to civilization.