The main reasons I think the "false flag" theory is nonsense are:
A. A huge amount of people would need to be involved, I would say at least 50, realistically hundreds. There would be a huge risk that someone would leak some info, and I don't think the risk would warrant the benefits. If any info was released, or sold to the press, there would be a full blown US revolution.
B. If the buildings were blown up, then why involve planes at all? Why not just blow them up and say it was the terrorists? It seems to me that there would be many easier ways to create a similar situation, without such complexities.
C. Why bother with the Pentagon? The gov wouldn't gain any advantage by blowing up the pentagon, as well as the WTC. I think the reason that there wasn't much info on the Pentagon incident at the time was due to embarrassment and security protocols - ie the US didn't want to admit that a plane could crash into it, and were scared of the repercussions of releasing too much info too early.
D. As I said earlier, the vast majority of the initial evidence for a false flag op has been thoroughly debunked, it seems that the only thing the conspiracy theorists say now is "But what about Building 7??". As far as I'm concerned, it's totally plausible that the building was affected by debris which caused it to fall. Unlikely maybe, but plausible, and certainly not a key piece of evidence for any conspiracy theory.
A. You are correct in stating that a fairly large amount of people would need be involved to pull something like this off. One thing you assume though, is that they all knew what the end goal of each of the roles they were playing were. It is called compartmentalization, and it is how military secrets are kept. We know it works because we used this same strategy to keep the Manhattan project under wraps successfully. The right hand doesn't know what the left hand is doing.
B. Plausible deniability, as well as scapegoating. How exactly do you explain how terrorists without domestic connections sneak enough explosives into one of the most secured buildings on Earth to blow it up? They tried in '93, it didn't work as well as planned.
C. The only wing of the Pentagon that was destroyed was the ACCOUNTING department, mind you this was one day after Donald Rumsfeld made an announcement that 2 TRILLION dollars was missing from the Pentagon defense budget. A lot of evidence showing where that money went was destroyed that day, along with all the people who knew anything about it.
D. No. Try doing some actual reading instead of relying on outdated half ass Youtube documentaries. Nothing has been debunked. There are still a lot of unanswered questions and inconsistencies about the official report. If you were right that all these theories have been debunked, why is it that many members of the original 9/11 commission report are now calling it a whitewash? Why is it that families of victims are still asking questions? Do you really think they aren't interested in the truth?