I dunno how long we should let this discussion go on, but anyway.... 
I found 9/11 horrifying. I still can't believe people could do something so terrible to other people. It was a terrible human tragedy. I refuse to reduce it to merely 'an attack on america'. It was a crime against humanity. It was something that should have brought us all together across the world, saying "my god how could something like this happen, how can we work together to prevent this?". And for a while maybe it did. But the nationalist spin that americans and the US government put on the tragedy was used to mobilize americans into the same 'us vs them' attitude the terrorists had. And the same willingness to kill thousands of civilians if that was what it would take to win.
As for the flag... the US flag means a lot of different things to a lot of different people. Burning a nation's flag- when done by people of that nation- is a strong form of government protest.
Burning an American flag doesn't mean that you want to destroy america, or hate america. It means that you feel the government, and the people perhaps, have strayed and disgraced what the flag and the country stand for. By burning the flag you are saying that THEY have dishonored it, that it has ceased to mean what it should. I wish that I could hold up an american flag proudly, that I could be something more than ashamed to be an american, but I can't do so in good conscience.
I don't see americans saying that the Iraqis shouldn't be allowed to desecrate their country's flag. For f**k's sake, we'd cheer them on. Are they entitled to more freedom of expression than we are? Do we take our country and our government to be so flawless that protest is inconceivable? And if a time comes when things get really bad, don't you want that freedom protected?
edit: btw, Gollum, great post eariler