Why? It is a waste of breath. It is an argument in which you will not prevail. You cannot convince someone that the Bible is inspired. I have tried. That dog won’t hunt.
There is a better way.
Just share what it says. Does not matter whether they believe it is the Word of God or not. Their refusal to accept the truth does not alter what is true. The Bible is the Sword of the Spirit, Ephesians 6:17. It is living and active and sharper than any two edged sword… Hebrews 4:12 – 13. Whether someone believes that or not does not change the nature of God’s Word… I could list more, but an illustration may serve us better here.
Say you were in combat with a broadsword. Say your adversary in this fight told you that he did not believe that your sword was real. How would you respond?
Would you go into a lengthy explanation of the origins of your sword? Would you tell him who made it and where it was forged? Would you extol the suppleness and sharpness of the blade? You might, but that would be epically foolish.
It would be much more effective to hit him with the sword. That would end the debate.
Just share the Word. Swing your sword, do not defend it.