9/11 happened because the Muslim majority refused to stand up to their extremists.. this is no different to christians not doing anything about the likes of the Westboro Church and other hateful christians... when the religious majority wash their hands of their extremist minority, they condone the extremist's actions with their inaction ...
this is the case because what is the first thing that happens when a non-religious person makes a complaint about religious extremists?
1) the religious majority either say nothing or
2) they say their extremists are not "true" christians/muslims/whatever or
3) even worse, the majority try to palm off the non-believer by saying that the non-believer doesn't know the believers religion so they should butt out
in ALL three scenarios described above, *nothing* is being done towards the problem of extremists by the religious majority, so the religious majority are irrelevant to the argument if they are not going to help fix the situation.
if there was no religion for these extremists to rally around, the extremists would just be a bunch of loser mercenaries with a chip on their shoulder, but with a religion behind them, like it or not, if the extremists are not dealt with, the extremists end up *owning* that religion....
look at all the christians who want prudish and stupid laws - imagine if they got their way, eventually those extremists would want people put to death for not believing ... and don't think that will not happen ... what about those gutless christians who make death threats against non-believers for being non-believers? what about the persecution of apostates (ex-believers) in many muslim countries?
no .. persecution like that can not be tolerated because eventually what happens is society ends up living in fear of being put to death for doing or saying the wrong thing .. that's not civilisation ... that's a prison ... the four-story prison walls are not necessary, because everyone is trapped in their minds by fear.
this is why separation of church and state is mandatory for any civilised society - it stops bickering in between religions so no religion can gain new recruits via coercion, violence or other nefarious methods, so separating church and state even protects the existing religious people themselves - imagine the outrage if 100 million USA christians were forced to become catholics in a catholic christian nation?
this is exactly how the dark ages happened, the majority did nothing about the extremist minority and that extremist minority who wanted to control everyone, took over christianity, and it all got out of hand, and then we had a thousand years of intellectual vacuum in the "western" world, due to the fear instilled by religion, having been hi-jacked by the extremist minority ...