Well, if you buy something and use it outside the parameters it was designed for, it is going to break. You are free to use it however you like but you did not designed it, someone else did.
What if a knife manufacturer wrote in his manual that you have to stab a human being with the knife at least once a week?
We're not talking consumer goods here. We're talking morality.
If you try to equate human beings with consumer products, you are simplifying the discussion way too much.
If a creator wrote in his instruction manual* for human beings 'kill unbelievers, even if it is your own child', would that be morally good? Why, or why not?
If he said "slavery is ok, as long as you don't beat your slaves to death and release Jewish male slave every after many years", would that instruction be morally good? Why, or why not?
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*) side note: if the Bible is supposed to be an instruction manual for human beings or life, it is hands down the worst manual ever! It has no decent and full description or explanation of the product, it is not arranged by topic, it has no FAQ, no trouble shooting guide, no safety instructions, no warranty. Many ambiguous and unclear statements. Some of the advice is contradicted by other advice. Nobody knows how to read this damn thing. Apparently we need priests, a Pope, LDS Living Prophets or a JW Governing Body to interpret and explain how this manual should be read? What a joke! Even those badly translated manuals for cheap ass Chinese toys, with incomprehensible and too tiny pictures are way better...