If you haven't read the New York Times (yes, the NY Times) article on this, allow me to summarize: they (the FBI) seek out potential terrorists and help them with money, encouragement or support. This is asserted to be part of a 'sting' operation to catch them in the act.
If you think setting up a conspiracy is not credible, then think carefully about how very close the above comes to arranging a terrorist attack. Consider how twisted people could push these 'sting' operations 'over the line' - and then claim that they are innocent - or that it 'just got out of hand' - or gain knowledge of when an 'encouraged' terrorist is going to attack and then set up their own attack, using the 'encouraged' as 'patsies'.
Here's one other thing to think about - the US started a war that cost hundreds of billions of dollars and (possibly) hundreds of thousands of innocent deaths based on trumped up accusations of 'weapons of mass destruction' that didn't exist - and didn't threaten US territory, even if they did. There are books and articles by CIA employees stating that the case against Iraq was bogus from the word go.
Was the war on Iraq a conspiracy? How could it not be?
metatron