I see this thread is getting a little old now, but it's contents have been of use to me so I think I'll contribute something back.
How to argue with a conspiracy theorist.
The answer (IMO) is not to argue with them, but state your position on the subject, and your reasons. Once you have done so, if they continue to press their point then they want you to believe what they do. I don't like it when people tell me what to believe, I consider it insulting. I make up my own mind. At this point I would politely explain that and also say that I had no problem discussing it but I had made up my mind about this subject, and their argument was unconvincing.
If you argue with them using the "facts" you play into their hands, as I'm sure any good conspiracy theorist would have atleast 1 conspiracy - oriented interpretation for each "fact" up their sleeves.
Facts aren't really good for arguing with anyway, because nomatter how trusted your source is, the truth is that they are always something that someone else tells you, and therefore subject to error.
If I were to attempt an argument with one such person (using building 7 as an example), it would probably go something like:
[CT]: building 7 collapsed symmetrically, i think it was deliberate, there must be a conspiracy
(crude I know, but words to that effect ^^ )
[you]: Are you convinced of this?
[CT]: Well just look at the "facts", courtesy of my source
[you]: So the official story doesn't answer your questions satisfactorily?
[CT]: its all lies, a building on fire doesn't collapse symmetrically according to this source that I trust more than the media
[you]: I don't think that is the case. Just because you have a question that isn't answered by the information provided to you via media agents who are not experts in the field does not indicate that it was all made up to make you believe something.
You can believe what you will, but I choose not to.
In order to stay on the high ground you just won, don't get drawn back into the argument. I've managed to pull this kind of thing a couple of times but the other party usually refuses to admit defeat, or ignores. all the same it seems to work.
I think that most people on both sides of this argument are out to make someone else believe what they do, for whatever reasons. Belief itself equates to faith without question... and so I would never say "I believe" to anything unless I was totally and utterly convinced.
I don't think you need to pick a side for everything. If some vaguely conspiracy oriented person started saying things like "did you know that 9/11 was a government job etc etc etc" that doesn't mean you need to deny or affirm. I stick in the middle for most of these things and when questioned about that, I tell them why.
My reasons are that 99 times out of 100, I WAS NOT THERE. I cannot draw on my own experiences and observations, and only third party media of mainstream or underground allignment.
When I am subject to this kind of stuff I usually remain quiet. Most of it also has no bearing on me so sometimes I say I don't care.
The point is, I'm not naiive enough to think that everything is as the official media story says, nor am I naiive enough to think that everything is not as the official media story says.
You don't need to have an opinion on everything.