All of those are ideologies with certain views on how the world is and how it should be, which can also said of religions.
If religions where purely spiritual and said nothing about the world then I would agree with you, but then I guess there wouldn't be any problems either.
Nobody is saying only religion leads to extremism.
When you recognize that I hope you also recognize that religion is the main cause (or tool) of extremism in the world right now, and that Islam plays the biggest role there.
