Here is my response (slightly edited for web use):
This guy is sharing some pretty crazy (though not original) conspiracy theories. These claims can be found on the internet, late night radio in the US, and are more common in Europe. These conspiracy theories are most popular in the Middle East where every tragedy/disaster is blamed on the Jews (the Jewish bankers and media moguls that are allegedly running the US and the rest of the world of course). I just saw a clip at MEMRI of a Yemeni professor on Arab Satellite TV claiming that Jews caused the tsunami disaster so that they could kidnap Muslim children in to the slave trade. This stuff is typical, but totally baseless.
On point one -
a- To believe this then there has to be a conspiracy of everyone at the top of the US government, Democrat and Republican. The bipartisan 9/11 commission published a report (which in book form has become a best-seller) that explored all this stuff.
b- We know that it was 19 Arab hijackers using our planes as missiles. If it were missiles not planes, then what happened to planes that were hijacked? We have hundreds of families that lost loved ones on those planes, what happened to those planes full of people if it were actually super-secret missiles?
c- We saw the planes hit the towers live on TV! Were we all hallucinating? We don't have a video of flight 77 before it struck the Pentagon, but we do have hundreds of witnesses, none of whom have any reason to lie. The missile claim is completely out of touch with reality.
d- So not only would all of our leaders have to be lying (and their assistants, secretaries, lawyers, etc.), nobody could ever talk or the truth would get out. As Ben Franklin said: "Three may keep a secret, if two of them are dead." This is the problem with pretty much every conspiracy theory, they necessitate too many conspirators. It does not pass the common sense test.
e- As for Korea, they do not have any Russian super-missiles. Check with Steve, he will confirm how silly that conspiracy theory is. (I added Steve's response below in this post).
On point two -
Osama Bin Laden himself has confessed to 9/11. It takes some very imaginative leaps to point the finger anywhere other than at Al-Qaeda. Again such a conspiracy requires just about every leader you can imagine to be in on it. People who buy this have a very dark, paranoid view of the world. This also defies the principle of Occam's Razor.
When multiple explanations are available for a phenomenon, the simplest version is preferred. A charred tree on the ground could be caused by a landing alien ship or a lightning strike. According to Ockham's Razor, the lightning strike is the preferred explanation as it requires the fewest assumptions.
I've heard a lot of these "conspiracy" theories over the past couple of years... but most have died out because they just don't have the kind of evidence to be supported. Apparently, this Brit has had his head in the sand the last year or so, or he's just got a really bad axe to grind. What did they call it in psychology... cognitive dissonance? Let me add one or two notes to what I believe was Theo's pretty thorough "slam" of the Brits' four points.
1. The Russian SS-N-22 "Sunburn" missile is an ANTI-SHIP missile... not an anti-building missile. It doesn't have the capabilities of a Tomahawk Land Attack Missile (which I'm guessing this Brit is thinking). It's launched (mostly) from ships against other ships, although there is an aircraft launched variant. At any rate, the sunburn uses an active radar system for its targeting/navigation. It would be a bit hard to pick out two buildings (as tall as they were) in the midst of all the skyscrapers in lower Manhattan. And oh, by the way, the warheads on these bad boys are only about 320 kg... enough to punch a hole in the side of a naval combat vessel, but probably not enough to collapse a skyscraper.
2. North Korea does not have the Russian-built SS-N-22 (although I bet they'd love to have them). Ever since the Russians cut "friendly" pricing in 1991, the North Koreans haven't been able to buy much in the way of Russian arms. Instead, North Korea relies on Chinese arms for upgrades. The principle anti-ship missile system the North Koreans have is the Chinese Silkworm missile (which was what was fired in 2003 off the Sea of Japan).
3. And, even if the North Koreans possessed the SS-N-22, I SERIOUSLY doubt that that would be the single reason that would preclude U.S. military action against the North. The SS-N-22 is a really incredible missile (with the newer SS-N-27 even more capable)... but, it's only a missile. At the end of the day, we're not going after the North militarily because of a lot of other factors... like the consideration of collateral damage to our ally, South Korea (just to mention one).
4. One shouldn't have to remind this guy that al-Qaeda issued several fatwa's throughout the 90's, declaring war on the U.S. bin Laden took responsibility for the terrorist actions in Saudi Arabia (Kobar towers), Yemen (USS Cole), Africa (bombings against US embassies), etc... And, oh, by the way, he claimed responsibility for the 9-11 attacks as well.
It seems that this conspiracy theory stuff is getting more popular on the left and it is being broadcast more loudly by the same old crackpots as well. I surf some of the popular progressive blogs and I encounter these type of outlandish theories often (usually the same ones over and over again). I follow the Rebecca Blood rule for the sites and blogs that are completely out of touch with reality: follow the same rules as one would walking down the street: "Don't make eye contact with someone who seems crazy." But paranoid conspiracies appear frequently in comments and discussions on left-wing blogs and sites that are operated by reasonable folks too.
Conspiracy theories are becoming more mainstream among progressives. Michael Moore's Fahrenheit 9/11 drew few conclusions directly about possible conspiracies (Bin Laden-Bush ties, Saudi-Bush ties, Afghan natural gas pipeline, etc.) though what he was trying to imply was apparent to anyone who watched it. It was amazing to me that Moore was almost universally applauded by members of the Democratic Party and was a superstar at the Democratic National Convention in Boston last year after making a film that made use of so many of the bizarre anti-US conspiracy theories. It is not all Moore's fault, he is more a symptom rather than the problem. The problem is that people want to believe -- or want others to believe -- the conspiracies more these days. Professor Noam Chomsky has had a following for his conspiracy theorizing for a very long time; but he is no longer a lonely voice, there is a chorus of people shouting like-minded claims now.
People on the left are not somehow naturally getting less rational, I think the problem is that leaders on the left were leveraging the political passion that comes with the illusion of a political crisis in order to mobilize activists, contributors and voters to defeat George Bush in the 2004 election. The prominent Democrats who applauded and endorsed Moore's film are smart people, they must have recognized that what Moore presented was not a reasonable picture of reality but believed that his version of the world could help them in the 2004 election. The Patriot Act paranoia, the military draft accusations, and the "Bush lied" conspiracy were all a part of an effort to energize people for what they felt was a noble cause: to defeat President Bush. The effort failed, and now they are stuck with the extremism that they nurtured. Howard Dean will likely be the next DNC chairman and the most active and organized are the most extreme in the party. While Senator Hillary Clinton prepares for her 2008 run for the presidency with a sensible effort to dash back towards the center and "triangulate" on issues such as abortion, she will be undermined by the extreme left in her party.
It is far easier to cultivate passionate, extreme views than to calm people down. The leadership in the Democratic Party did far worse than just lose an election in 2004; by winking at paranoid conspiracy theories that temporally directed political energy in their favor they steered their party down a dead-end street. The intense pitch of their extreme activists can not be sustained by claims of doom that will never materialize, and the message and language of conspiracy extremism will turn off the moderate voters who will be needed in order to win future elections. Those leaders in the Democratic Party that do not already regret the 2004 strategy are bound to come to regret it in the future.