Root cause of terrorism: in fact the left and right both agree about the root cause of terrorism—oppression. They just disagree about the identity of the oppressor. The left thinks it is the West/Israel/Capitalism. The right thinks is the regimes themselves.
But the real culprit is the UN. The UN and its system is what gives these thugs whatever legitimacy they have. The system that insists on treating all regimes as morally equal is what keeps the people of the Arab and Muslim countries in the totalitarian prisons we insist on calling nationstates.
That is why working with the UN to gain legitimacy is a mistake in the long run. In the long run it just gives more legitimacy to a corrupt world order of incompetent Third world thugs and their creditors, all in the name of human equality. If colonial powers ran such brutal and extractive governments we would all be appalled and ready to fight to free these people. But dress them in nice suits and seat them around that nice UN emblem at a big, important looking table and suddenly they are spokesmen for their own victims.