Irish comedian Dara O'Briain first used the phrase in his stand-up performances when talking about priests, astrologers, and the like. He said that he would put them all in a big sack, tie the sack up with string, and hit them all with sticks.
He then went on to say that when someone gives a facile answer to a difficult question, and that person is then asked to provide evidence, but replies with "There's more to life than evidence," the proper response to that magical thinker is "Get in the fuckin' sack."
Oh, the good people go to live with god, and the bad people suffer for all eternity.
What's the evidence for that?
It's in the Bible.
Get in the fuckin' sack.