A full investigation of the banking system would cause credibility to be lost by the banks which would unravel the whole system as the fractional reserve system collapses. Thus the government needs to remove credibility from those who pose a threat to this system.
As to why white supremacists aren't targeted, white supremacists don't pose any fundamental threat to the banks or to power because their ideas are unpopular, occupy touches upon an angry thread running through the country that the average person cannot get ahead. Threads like these unseat governments, an unseated government cannot prevent an investigation into the banks.
Edited for some grammar & clarity.
For sure, the powers don't stem from the Fed but the reasons do.
It could be as simple as the Occupy movement represents a target rich environment.
I meant economic in more of a generalised "freakonomics" sense.
Are you implying that there aren't enough of these groups to justify their budget, so they have to invent them? This is indeed the obvious conclusion. I was wondering if anyone with more knowledge of the specifics could dream up something more juicy...
I still think the tactic is unethical, but this is one way it could be effective.
So basically, nothing that terrorists do is illegal until they actually go out and try to kill someone. The FBI can use a person's history of lawful activities to find people who match the profile of someone who is highly likely to commit a terrorist act in the near future and offer them a fake bomb and a ride to the nearest synagogue. When that person pushes the button, that establishes the intent to commit a crime. It's no different than going up to a guy the police think is a drug dealer -- because of the clothes and the way he acts and other lawful activities -- and asking if he'll sell them any drugs. It's not entrapment unless the police really screw up their approach.
As for the economics, consider the alternatives. Waiting to see if the terrorist would use a real bomb carries a high risk, and the terrorist would be less likely to be convicted than in the case of a FBI-provided fake bomb. The court system has exonerated terrorists with strong evidence against them like Sayyid Nosair and Sami al-Arian because they claimed to have been oppressed and persecuted for being Muslims and found sympathetic juries. The fake bomb plots with their careful establishment of identity, motive, and criminal action have all gained convictions.