I simply fight BD - Courage decks with… another BD - Courage. XD
Edit: I mean until they review the guardians, mirroring the enemy deck usually work as counter, including BD - Courage. I personally also think that Courage and Justice need to be toned down a bit. And yonizaf explanation was on point too. Though devs said they will review guardians after they nerf Bone Dragon first, God knows when.