I can't say I've looked into the situation in very much detail, but there are always two aspects you have to look at when trying to prove something controversial.
1) What is the evidence that it is true? I'm not touching this with a ten foot pole.
2) Why would they do this?
The second one is more important, because I highly doubt there was a conversation that went:
"I'm bored, Mr Cheney. What should we do today?"
"Let's go blow up one of our own buildings"
"So we can spend several trillion dollars on aimless wars, with the result that everyone will hate us for eternity, so we can deprive out people of civil liberties, so that we can kill some Saudi guy living in Afghanistan minding his own business. Fun, right?"