Actually, Jedi was referred to as a religion TWICE in ANH.
Han Solo: "Hokey religions and ancient weapons are no match for a good blaster at your side, kid."
Grand Moff Tarkin: "The Jedi are extinct. Their fire has gone out of the universe. You, my friend, are all that remains of their religion."
There was also the line: "Your sad devotion to that ancient religion hasn't helped you conjure up the missing data tapes."
Anyway, I am not certain whether the referenced religion was made up only of the Jedi or of all believers in the Force. If it was the latter, you didn't need midichlorians to join.
