On Blasphemy

Which do you suppose is more genuinely offensive to God - an unbeliever who, in a moment of pain, anger, or frustration unthinkingly uses an English word, also used to designate God, as a curse, or professed believers who routinely speak of the ways and purposes of God with such matter-of-fact certainty that one would think they "own" Him the way the mob "owns" a Judge, like a lab rat sliced open and pinned down under their microscope, all His secrets revealed?