You're making the argument that cultural relativism is wrong. I'm making the argument that cultural supremacy often leads you to wrong reasoning about causes and effects, and ergo, bad policies. Are the Palestinians committing terrorist acts because they're Islamic? They're relatively more secular and cosmopolitan than some other Muslim communities, and Palestinian Christians also commit violence. If you ascribe their violence to religious grievances alone, then you are in a quandary. There's no way to solve the current situation without changing their religion. But if you recognize it as nationalistic and a response to geo-political grievances, then there is a political solution that may not require millions of people to be reprogrammed to a different religion.
Imagine if we ignored the Holocaust, and simply ascribed Jewish terrorism in the British Palestinian territories in the 1940s as a manifestation of Judaism -- that God gave them this land? Under that interpretation, it's scripture, and not the reaction to historic persecution, that drives the motivation to carve out a Jewish state. And yes, some far-right Jewish extremists believe this, but that's not the majority, and so you can't paint all of Judaism in this way, and we don't.
But we do paint all of Islam this way, and as a result, we engage in bad, immoral foreign policy.
This is the one single point that is very hard to accept by the mainstream. Currently, the doctrine of all cultures being equal is something universal. If we accept the opposite view, there are many dangers on the way. Who is going to decide which culture/religion is better? By what criteria? What are the consequences? It's safer to declare equality, and this is what happened in the West - and any attempt to question that is perceived as a regressive view.