Two major arguments I have.
1. In general, rules cannot be selectively followed, or it defeats their purpose. The whole reason rules exist is because humans cannot be trusted to decide for themselves how to behave.
But selectively following rules means that humans get to do just that, and rules have no power. So, if people choose to ignore the rule in the bible about [not mixing fabrics](http://biblehub.com/deuteronomy/22-11.
htm), then they can justify ignoring rules like don't murder, because of the precedent.
2. The bible is accepted based on faith that the word of God is infallible.
If you believe parts of the word of God are false, than you are rejecting the premise that it's infallible, and thus there's no reason to believe in any of it.
If you contend that parts of the bible are metaphorical, or were modified from their original text, then you open up the passages that you do believe in to the same criticism.
I'm not trying to be an /r/atheist-esque religious basher, or anything. I'm just genuinely curious how this is reconciled.
And I'm very open to the possibility that I'm misunderstanding what 'faith' means, since I've never really had it in my life.