Even if it is, it would make more sense to use the good parts / good morality found in the Bible to reason with those who are still die-hard believers, rather than alienate them completely by telling them it's all shit.
What parts are those? The part where Jesus killed a tree for behaving like a tree? The part where he called people horrible names and predicted their death? The part where he said he was there to cause families to fight? The part where he was killed for sedition?
Which morality, exactly, are you claiming is unique to the Bible that we should use?
I actually have come to value kindness, hope, and love equally as much as truth. If there is no God and there is no afterlife, with no judgment on whether I believed in facts or falsehoods, shouldn't kindness and happiness take priority over truth?
Here's an example. A child is at risk for a disease. The only vaccination or preventative measure is via injection. The child is deathly afraid of needles. Should the parents, instead of recognizing the truth that the child could get ill and die, be kind in the moment to make the child happy and refuse the preventative measure?
If you don't like that example, please come up with one where kindness and happiness are more important than truth.