Bible is not infallible in morals.
Lets examine the commandments.
thou shall not kill
Can anyone explain why person shouldnt kill others?
thou shall not steal
Can anyone explain why person shouldnt steal from others?
Do not commit adultery
Why shouldnt person commit adultery?
thou shall not bear false witness
Why not?
honor your mother and father
Why would one even do that?
If your answers to any of these are "Because God says so", that is no different from saying "Because I say so".
If your answer is "God always says what is correct / God is always correct", that is not only unproved but even unlikely.
However, if you try to base these morals in some objective logic, a simple problem arises, that any objective logic supporting these morals doesnt support the Bible.
Lets take as example "Eye for eye" (considered objective morality). God of Bible orders killing of people who killed no one, orders killing of gay people, killing of people who wear different clothes.
Now, you can either say killing of gays is fine, hence violating Bible's first commandment, or you can say its not fine, and then admit Bible is wrong.
Further, a morality of eye for eye pretty much leads to body autonomy argument, which Bible at the same time denies.
Further, anyone who claims "We are owned by God and thus dont have body autonomy", well, in that case, there is no morality either. If God can kill people randomly, which God does, then he violates the very commandments he asks others to uphold.
If God determines morality, morality doesnt exist because God can just change it at will. And if God doesnt determine morality, then the question rises "What does?".
the problem with Bible is very simple. there is nothing to deduce morality from. If you deduce it from "Eye for eye", you end up contradicting the Bible. If you deduce it from "Because God says so", that is not morality, but just God's opinion which he can change at any time, and also has no justification for.
So in order to deduce morality from something, something must already contain morality, but logically, there is nothing which contains morality to deduce morality from.
there are attempts at self-contradiction, but we must first explain what self-contradiction is. Self-contradiction is simply trying to hold two statements both as true, while they cannot be logically both true.
So, in a sense of: A or not A. But Not A produces contradiction, so A true.
the issue, however, is that no one so far did this for morality, not further than lex talionis at least.
this is simply because, if something was self-contradictive, it would be impossible to do. So if certain action was self-contradictive, to do such action would be impossible in the first place.
So any morally wrong action wouldnt exist in the first place, if morally wrong action was self-contradictive.
What lex talionis does, is not prove what is good and what is wrong, but it functions under logic that if killing is okay, then punishing a murderer with death is okay too, and if killing is not okay, then murderer is wrong in his actions and thus can be punished for them.