See the MIT paper linked from a lower ranked answer - they can actually amplify the radio waves, by as much as 30dB! That's a 1000x increase. Now that's a proper conspiracy - to cause people to wear those in order to amplify the effects.
True, it blocks some radio waves and amplifies others. But maybe it amplifies good mind-control signals and diminishes bad ones? Only one way to find out! adds 32 rolls of foil to cart