If you look out your window you will now see that we are flying 5000ft above GG's head.
What it means is that the "foil hats" is derived from conspiracy nuts thinking that the CIA had the capabilities of reading their minds to gather intelligence. Because of the publicized short falls of the CIA in gathering intelligence these nut jobs now realize that they don't have that sort of capabilities and are now at ease to walk around foil hat free.
Otherwise put, it's a dumb joke.