1 Drop of Cyanide doesn't sound like much but if it is in high concentration it will kill you. When 1 drop is followed by another and another it will kill everyone.
By the time you add Sodium Thiosulphate, it's too late, the Cyanide as done its damage...
So 1 drop of Islam doesn't sound like much, but if the Islamist is fundamentalist (high concentration)...blah blah you get the analogy....