Well I just watched 9/11, it was not quite as shocking as BFC but still some things were pretty nasty to watch, like the US soldiers getting bombed etc.
It's not
that hard hitting to me personally because I've seen a lot of documentaries about 911, Bush, the Iraq war etc and I know what the Bush regime is like (look for something called "Bush Family Fortunes" by the BBC) - that said, some things that were revealed in 9/11 were pretty scary.
No doubt the FBI are watching Michael Moore's every move now...