There are plenty of websites and television shows that specialize in credibly debunking the various MIHOP theories. What remains to be seen is an effort to dispel the LIHOP theory. So, why couldn't the 9/11 attacks have been allowed to occur?
One of the major flaws with LIHOP is it's not something the administration can do. The administration are not responsible for preventing terrorist attacks - the various government agencies are. So LIHOP actually requires the largest number of collaborators, because it requires entire government departments to be in on it. The FBI, NSA, CIA, DoD... they all have to be in on it for LIHOP to work. In fact about the only people that don't need to be in on it for LIHOP to work are the Administration. Just my opinion.
I personally don't see a significant motive for either MIHOP or LIHOP. Truthers like to say the "government" let/made 9/11 happen to invade other countries. Well, the excuse for afghanistan was a pipeline between Turkmenistan and India.. which (a) still hasn't been built, and (b) has absolutely no benefit to the US. The excuse for Iraq was for oil, except all the major oil contracts went to China and Russia and the US are still economically struggling while paying over $100 a barrel to exceedingly wealthy oil companies. But apparently this was all worth 9/11... I don't think so.
nothing of it makes sense unless you are a conspiracy theorist who is always looking for a conspiracy everwhere you look. The US didn't benefit at all from 09/11.. The twin tower collapse hit the economy hard; trillions spent on wars which has added to the defecit/debt problems; thousands of americans killed; rise of anti government conspiracy theorists; chaos in post war Iraq with more Islamic radicals rising; Afgan a mess post war; no big benefits on the Oil front for the US. 09/11 only made matters worst for Americans and the government so if they let i happen, it was a big miscalculation. Not to mention that IMO, it would've been impossible for everyone in all these government agencies to be involved and cover it up. No way that the FBI, CIA, NSA and the Bush administration would've conspired to do this and all of the hundreds involved would've prevented their guilty conscience from speaking up. Come on guys, do you guys sometimes just stop to think how ridiculous this is? I'm much more inclined to read into conspiracies about the US allowing Pearl Harbor because this was WW2 and Hitler needed to be stopped. Even so, there is no credible evidence that the US allowed it, the Japanese planned it well.
They don't debunk those theories which are really facts now. They just try to obfuscate the proof of an inside job and then consider it debunked. Anyone who actually studies the proof will see that those websites don't come close to debunking the facts. Here is a link to some of the facts. http://www.politicalforum.com/showthread.php?t=334129&p=1063367099#post1063367099 As of now this link works.