Islamist might best be understood as monocultural supremacism.
The opposite of the idea that there is One Big Unchanging Truth is not “There is One Big
Unchanging Truth and it is that there is no Big Unchanging Truth.”
Being confused about this seems to me to be close to the heart of our philosophical troubles over the past few centuries, which themselves underlie all the solvable political problems which never get solved.
The opposite is that there are, at any given time, knowable absolute truths, but that they are confined to time and place, which is to say SPECIFIC problems, for specific people.
I am tempted to say that prior to evaluating any aspiring philosophers ideas, one needs to know how they use their body, how much physical tension they carry, what types of brainwaves predominate. In our present era there seems to be a strong correlation between high intelligence and stupid counterproductive beliefs. Our culture, outside the realm of science, has largely lost the ability to select for the best and the Good.
This is not the fault of the masses, but rather that of confused and confusing intellectuals.