I reiterate a point I've made before that I think conspiracy theorists secretly want the powers that be pulling all the strings behind the scenes. It's so much more comforting to know that everything is part of some greater plan, rather than acknowledging that sometimes random, tragic events just happen out of the blue and they can't be prevented. I mean, I certainly know the feeling - in tragedies in my own life, I've thought to myself, "Well, if only we had done this and that, maybe it could've been avoided," but then I'm faced with the reality that some things are completely random and beyond anyone's control - it's just wishful thinking to say otherwise.
To say that, for example, the government is responsible is to say that if we stop the government or whatever, we can prevent horrible events like this. If random groups of people, however, can pull off something like this, then we have to acknowledge that these sorts of things are just a fact of life and there's always going to be a risk for them.
That said, yes, I'd prefer if we didn't make such a huge friggin' deal about 9/11 every year. Yes, it was horrific and tragic, but we all remember it, we all watched it while it happened, we don't need those memories repeatedly dragged up. We've made a lot of bad decisions as a nation in the years following 9/11 driven purely by emotion stemming from the attack. Keeping that pain and fear alive only further fuels that. I mean currently, we've got the whole Syria issue, which is extremely complicated and there are no easy solutions, and the last thing we need is our minds clouded by any of that.