Sin as a concept is even one the religionists struggled with (and failed in defining, or at least squaring with the idea that its definition emanates from a divine source).

Once the concept was introduced that sin itself is atoneable, a big feature in christianity but common to most religions, then the need arose to start grading "sins" on a scale of severity. Of course once they did that then they acknowledged that "sin", whatever divine moral authority they think might have ordained it, was simply that which all societies had always understood as a crime against moral standards - a very much more human thing and one moreover that underlies the concept of "crime" as we understand it today and the easily understood principle that crime itself is gradeable.

But if I read your original post correctly then you are complaining about the almost subliminal use in everyday language of phrases and words that have no real meaning except in a religious context. I would argue that a lot of this terminology has sufficiently distinct semantic meaning to infer that the opposite is the truth - it is the religionists who have "hijacked" perfectly proper terms semantically (if sometimes a liitle vague in meaning) to their own ends. By using them as an atheist I am simply claiming them back, dusting them off semantically, and setting them back to their original job.

And besides - even blasphemy, a concept that has almost no value whatsoever outside of a religious context, has had its uses. Thanks to centuries of its application I can, as an atheist, shout JESUS FUCKING H CHRIST! when I hit my thumb with the hammer and (though not at the time) offer a little vote of thanks to generations of the delusioned for imbuing such a quirky and semantically impoverished set of phoentics with such virulent expression of anguish, anger and excruciating pain.