Because everyone who approaches the Bible does so with a sense of what's important and what's not — and, based on that, latches onto passages that they consider (or have been taught are) important and pertinent, and Commands from On High … and disregards passages that they think are trivial, no longer important, puzzling mysteries, and/or historical oddities that can be set aside.
The issue becomes (a) awareness and acknowledgment of it, and (b) what you then choose to pay attention to, and why.
I'll be the first to admit that — and that the messages I find in the Bible that I think are both illustrative and (to me) compelling are those of love for others and a focus on personal morality in the context of a greater society. In so doing, yeah, I disregard or dismiss a lot of things I consider as historical or cultural baggage from the writers. And, yeah, some might consider that some sort of confirmation bias (look, the Bible supports what I believe already!), but, then, I also don't consider my personal beliefs to be perfected universal diktats for all to obey. #ddtb
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God Hates Cretans? (and other passages of Scripture we’d rather not talk about)
As part of our series on learning to love the Bible for what it is, not what we want it to be, we’re working our way through Christian Smith’s book, The Bible Made Impossible, In it, Smith tackles the…

The epithet “Cafeteria Catholic” comes to mind…
True. But it applies to all denominations, and faiths, and ideologies in general — self included. And that can be a good thing, if it indicates actually *thinking* about what you’re believing in and rejecting the stuff that doesn’t make sense (and a bad thing if it’s a matter of simply choosing an easy course).