The Islamist terrorists would be deprived of a meaningful reason to kill people in the name of implementing Islamic law if their political brethren got to take over entire countries and implement Islamic law. Once the Muslim Brotherhood took over a few countries, then Al Qaeda would be marginalized and irrelevant. Its operatives would soon have to drop the terrorism and get jobs teaching about LGBT rights or building solar panels.
Whoever came up with this plan probably had a grandfather in the State Department who said in 1919 that the Communists would become less dangerous to Western Europe now that they had all of Russia to use for their economic experiments because stupidity doesn’t go away. The same old ideas that cost millions of lives a few generations ago are repackaged with some artful worldplay and are parroted by the smart set as the sort of thing that should be obvious to anyone.
Islamism, now joins Communism and Nazis on the shelf of things that we don’t really have to worry about once we’ve appeased them enough, at least until they stop taking off fingers and start biting off hands and then suddenly we have to start worrying all over again.