If you are half way educated you don't need a source.
These are all historical events that were conspiracies. Just because some of them weren't known as conspiracy theories by outsiders before they were exposed doesn't mean that people in the government were not lying to us and participating in a conspiracy.
Also the Gulf of Tonkin incident establishes that the government will lie to the public to foment war. Which is exactly what 911 was.
Look, you are correct in that I wouldn't expect someone making a persuasive argument to cite a source for something like the Gulf of Tonkin Affair, since (as you note) it is a commonly known historical event.
However, when the author then makes statements that world policy is managed by a select group of elite individuals controlling banks and all resources, I would expect the author to, maybe, back up the claim with a source or two.
Many of these conspiracy ring leaders use a persuasive tactic I tend to see a lot in extreme political ideologs. They assert a well-established fact, something that people can buy into, like Gulf of Tonkin, Iran-Contra, etc. Then try to pull people a long into fringe theories and outrageous assertions. Not really a whole lot different than Rush and the like.