Why shouldn't the forums (and bitcoin overall) be shut down? Why shouldn't a central authority be set up to tackle the frauds that are so endemic in this community?
Central authorities do little or nothing to eliminate real frauds.
Healthcare fraud in the United States amount to something like $100 billion a year.
If you added all fraud from government programs it would be much higher.
The collective fraud of central authorities is much worse than the fraud contained in bitcoin or other alt currencies which are still in their infancy.