Morality predates the Bible
ergo we did/(potentially)do not need the Bible to become moral beings.
Objection A: As was God’s intent, we are by nature moral beings, but through Adam we fell from grace; the Bible is simply a means to furthering our moral growth in an already fallen world.
Response: The Bible is not a moral book. The OT is littered with hideous accounts of divinely justified murder, contempt and misogyny. Four of the ten commandments do not deal with interhuman conduct but reek of divine egocentrism; the rest are suspect. The NT answers for these moral deficiencies of the OT by introducing the doctrine of salvation and the threat of hell.
Objection A.1: The OT is not immoral.
Response: Yes it is. If genocide, slavery and murder are considered immoral then by inference so is the OT.
O: How can you establish that if you have no objective set of morality?
R: How can you establish that the OT is moral, since your premise of God’s existence is susceptible to refutation?
Objection A.2: Jesus said many good things in the Bible.
Response: The bad things in the Bible contradict with, or often outweighs, the good. If the Bible is moral then I daresay so is Mein Kampf.
Objective A.3: You are taking the Bible out of context.
Objection B: The Bible teaches salvation. Man is by nature sinful and only through Jesus Christ can we be saved.
Response: The OT is still immoral. The fact that old laws are replaced by new ones does not negate the charge of immorality. The NT avoids the moral question by superseding it with an eschatological one, conceding that we cannot by our own work redeem ourselves. Therefore the Bible still does not have a monopoly on morality.
Objection C: The Bible was the first book to properly addresses moral questions.
Response: See Grecian philosophy. See Buddhism. See Confucianism.
Objection C.1: The Bible was the first/only book of morality authored by God.
Response: It says so in the Bible.
Objection D: Without the Bible there can be no objective set of morality.
Response: Your claim to objectivity hinges upon highly dubious and subjective premises. A Muslim could easily use the same argument with the Quran, and he would sound just as convincing, ie. not too convincing at all.
Objection E: The way to God is by faith and faith alone. In other words, whatever you say, I shall still believe that the Bible is the inspired word of God.
Response: I know, which is what worries me.
Objection E.1: God works in mysterious ways. Sometimes he orders genocide. Sometimes he orders children and babies to be dashed to death. Sometimes he orders a bear on unruly youths. Sometimes he orders people to be stoned to death for seemingly stupid reasons, like gathering sticks on Sabbath. Sometimes he punishes people for their sexuality, after having created them so. Sometimes he commands circumcision. Sometimes appears to condone slavery and misogyny. After all, who are we to question his will?
Response: I rest my case.