This is the answer I gave on Facebook in a discussion on this exact topic, thanks to Chris DeMarco for starting and hosting this thread:
As a student of Comparative Religion and having read many scripture of many differing religions, including the Bible and Quran, one of the things that becomes obvious is that scripture must be placed into the context of the cultures in which they were written.
The Old Testament was written in the cultures at the end of the Bronze Age, including Nomadic, Judaic (as in the kingdom) and Egyptian amongst others. The New Testament is written from the cultural view of the Roman Empire and the Quran from the 7th Century culture of Arabia.
Many followers of these religions think the rules and regulations that are handed down are the laws by which man is to live by for the rest of time, no. They are all examples of what constitutes a moral and ethical life in the times and places they were written.
For example, the slavery references are for their day. Today most of the world finds slavery to be abhorrent, but how one treats their slaves in a world where it is common-place, can be done ethically or not. When you place these "laws" into culture and time, they make sense, to a degree. Outside of their context, they seem primitive and they are.
Of course one day, the things we think of as "normal", moral and ethical may well be fairly primitive to our descendents, will we attempt to enforce our cultural ideals onto their world? We'll see when the next Religious Avatar comes along and creates the next great religion.
What most people are unaware if, is that there are two kinds of truth. Truth with a capital "T" is the ultimate Truth, it is the non-changing Truth, no matter what happens. Truth with a little "t" is the truth that changes, based on time, place and situation.
For example, Truth with a capital "T" is that you are a spiritual or energy being having a corporeal experience in a physical body. This Truth never changes, it truly is eternal.
An example of truth with a little "t" would be that you are having that corporeal experience in the Roman Empire, with slavery is part of your daily existence. How you treat those slaves in a moral and ethical fashion becomes truth with a little "t" because slavery will cease to be acceptable in the world that you live in, it is changed.
When looking at religion or scripture, remember that the Truth is always in there, even when it is obscured by the truths of the time and place it is written.