One of the main problems is that there is not one single, coherent statement in the bible that explains what the real rules are. What laws are to be followed by all people in all times and all places? Which laws are the most important? Which laws are dumb and can be ignored? And if there are laws that are not that important, or not relevant to all people, or are stupid, then why the hell are they in the book?
We know that stupid laws make it onto the books. Apartheid, for example. It is illegal to whistle while carrying a rhesus monkey in Vermont. (Not a real law that I know of.) You can shoot a gun at someone if they make you nervous in Florida. (Unfortunately, a real law.)
We expect people to make dumb laws and to have to go back and change them later. 'Cause people don't know everything and we make mistakes. That's why the US constitution is so long and complicated. We keep having to fix mistakes. People spend their legal careers figuring out what it all means for modern people today. But the constitution, a flawed human creation, is still nowhere near as long, pointless, convoluted and ambiguous as the bible.
We don't expect a god with all the knowledge and power in the universe to make mistakes. It makes god sound like a Monty Python character...
God, played by Michael Palin in a funny pope hat: "Kill all witches, gays, rape victims, sabbath-violators and Canaanites. No, scratch that. My bad. There aren't really any witches, and killing rape victims is just horrible. Just kill non-believers. And murderers. And gays. Yeah. That's it. No, wait....don't write that down yet. Let me think...."
Is it any wonder if we are a bit skeptical that the bible was inspired, written or in any way related to an all-knowing, superhuman supernatural being? It's too full of crap.