Quran tells Muslims to kill the disbelievers wherever they find them (2:191). So whereeve you find people who doesnt believe in Islam should be killed. Even if the disbeliever is blind, handicapped, kid who cannot understand religion or god fearing girls or old women who believed for ages in some other faith. whatever way you try, you cannot justify this. Why allah who knows everything has to say something like this generally? And how can you justify 90% of all terrorist activities happening all around the world?