There are Muslim fundamentalist groups with terrorist cells in control of areas and seeking to spread their influence in:
* Iraq and Syria (ISIS)
* The Philippines
* Western China
* Nigeria (Boko Haram)
* East Africa (Al Shabab)
* Muslim controlled neighborhoods in Europe where they attack women who aren't veiled, tell locals not to walk dogs, desecrate churches without penalty, attack homosexuals and Jews with little consequence
We are already in a world war of fundamentalist Islam versus everyone else, though that is a faith that spread entirely by the sword except for Indonesia for its entire history from the day Mohammed was rejected as Messiah in Medina and said no more peace, raid the caravans for loot and it is moral as long as Mohamed got a cut.
Islam even justifies terrorism - the greatest good in the faith is spreading Islam, not life. So killing 1 to scare 10 into converting to Islam is moral.
Committing one or two atrocities well publicized to scare people who see it into submitting to dhimmi status (extra taxes, fewer legal rights, live under laws that privilege Islam so you want to convert) is thus moral, because spreading a legal system that pushes Islam is almost as good in the Koran as outright conversion. You see this in the mass sexual assaults across the EU New Years Eve 2016 and at other events - to scare women into submitting to Islam's dress code and behavioral rules, while rewarding Muslim men who are told they have the right to rape any woman not covered up. It is, in essence, showing who is "boss" while scaring the rest into behaving like Muslim women (in burkas if out at all).