I see atheists attacking scriptures for several reasons:
- They can and do attack the idea(s) of God directly, but attacking the "word of God" is something else that can be done.
- It's sometimes (not always) easier to attack scriptures than the God idea.
- It's especially fun because of the large number of people who won't concede there are ANY mistakes.
The hope is that they can convince themselves and others that the writers and followers of the scriptures, people who claim to be God's servants and friends, were and are idiots in this belief. Being that the "prophets" and "saints" were idiots, some of the primary reasons FOR believing in God vanish away.
Your warning of futility
> I see the quest to prove the non-existence of
> God as completely futile
sounds like Sagan's character who claims to have an invisible fire-breathing dragon in his garage. Whatever argument you give him, why the evidence suggests he doesn't, and why he probably could not have such a creature there, he can come up with one or more reasons (usually irrational) to defend his claim.
You could be right, maybe it's futile. The hope is that the free-thinking theist will think himself out of this absurdity. I know it's possible because it happened to me.
Why should a rational person go through this self-defence mechanism of keeping a belief in God? Give up on the tooth fairy, Easter Bunny, and Santa Claus. Don't look for stretched reasons TO believe if realistically there aren't any. Give up on God. Don't look for loopholes in science that seem to allow for some attributes of God to exist if there really aren't good reasons TO believe in God.