For god-fearing religions, the only reason to be moral is the child's concept of morality — be good or you will be punished. For healthy non-believers, we can see that altruistic behavior and morality grow out of the knowledge that making others happy makes us happy.
How do you know the difference between right and wrong WITH the Bible. The Bible endorses genocide, slavery, rape, incest, human and animal sacrifice (i.e. Jesus and ritual sacrifice of animals), and many other evils. People often pick out what they think is good and ignore the bad.
Even the mythical Jesus in the Bible is not a good source of morality:
Matthew 10:34
"Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword."
Matthew 10:35-36
"For I have come to turn a man against his father, a daughter against her mother, a daughter-in-law against her mother-in-law — a man's enemies will be the members of his own household."
Luke 12:49-53
"I have come to bring fire on the earth, and how I wish it were already kindled! But I have a baptism to undergo, and how distressed I am until it is completed! Do you think I came to bring peace on earth? No, I tell you, but division. From now on there will be five in one family divided against each other, three against two and two against three. They will be divided, father against son and son against father, mother against daughter and daughter against mother, mother-in-law against daughter-in-law and daughter-in-law against mother-in-law."
Luke 14:26
"If anyone comes to me and does not hate his father and mother, his wife and children, his brothers and sisters — yes, even his own life — he cannot be my disciple."
John 15:6
"If a man abide not in me, he is cast forth as a branch, and is withered; and men gather them, and cast them into the fire, and they are burned."
Matthew 18:25
"But forasmuch as he had not to pay, his lord commanded him to be sold, and his wife, and children, and all that he had, and payment to be made."
Matthew 24:45-51
"Who then is the faithful and sensible slave whom his master put in charge of his household to give them their food at the proper time? Blessed is that slave whom his master finds so doing when he comes. Truly I say to you that he will put him in charge of all his possessions. But if that evil slave says in his heart, 'My master is not coming for a long time,' and begins to beat his fellow slaves and eat and drink with drunkards; the master of that slave will come on a day when he does not expect him and at an hour which he does not know, and will cut him in pieces and assign him a place with the hypocrites; in that place there will be weeping and gnashing of teeth.
Luke 12:42-48
And the Lord [Jesus] said, "Who then is the faithful and sensible steward, whom his master will put in charge of his servants [slaves], to give them their rations at the proper time? "Blessed is that slave whom his master finds so doing when he comes. "Truly I say to you that he will put him in charge of all his possessions. "But if that slave says in his heart, 'My master will be a long time in coming,' and begins to beat the slaves, both men and women, and to eat and drink and get drunk; the master of that slave will come on a day when he does not expect him and at an hour he does not know, and will cut him in pieces, and assign him a place with the unbelievers. "And that slave who knew his master's will and did not get ready or act in accord with his will, will receive many lashes, but the one who did not know it, and committed deeds worthy of a flogging, will receive but few. From everyone who has been given much, much will be required; and to whom they entrusted much, of him they will ask all the more."