I'm sure you're right that religion plays a role, just as it played a role in what Christians did to others some time ago. I think the main difference between Tibetans and Muslims is that there are fewer Tibetans, their target (China) is a totalitarian state with enormous security apparatus, and they have much, much less money since it's difficult to drill for oil in Tibet. Regarding the biographies of 9/11 hijackers, I've read somewhere that suicide bombers don't avenge the wrongs done to them but rather those done to their community. Really, it's a bit ironic (in a very sad way). Muslim emigrants from war-torn Middle East are rarely welcome in other, wealthy and peaceful muslim countries, so they are forced to come to Europe and USA. There they can live well enough to have the time to start thinking about how much their respective country/city/neighbourhood/family/any other community they identify with has been wronged by the greedy westerners. Some of them, with a bit of religious radicalization, will act on it - against the country which has given them shelter.