Usually used after a fact or bold statement.
Asshole: "A large meteorite struck the earth, according to theory."
Or for even the more practical use:
Dude Who Wants To Gain Knowledge: "Hey what time does the movie start?"
Asshole: "7:05 according to theory."
Dude Who Wants To Gain Knowledge: "No need to be a douche"
Asshole: "Come at me bro!"