Debate: Closing response on Christian Sexual Morality

I want to thank Justin for taking the time to have this debate.  Justin's closing is here.

I feel both cheated and cheating: cheating because I had both the first and last post, cheated because Justin has a slightly unconventional view of Christian Sexual Morality but, in his favour, he does try to defend the conventional view and never resorts to the argument from authority 'my God said it so it must be right.'

I have commented on Justin's individual posts to try to tease out what I think his central theme is and his views on certain aspects of standard Christian views.  I will try not to focus on too many of these but I think his views on homosexuality have to be examined.

Justin redefines traditional marriage to fit his argument: marriage is purely about the right/obligation to have children.  His arguments against homosexual marriage then goes on to cite dubious statistics from a single study which found that children

 were 70 to 100 times more likely to be killed by a stepfather than by their biological father.

A shocking finding to be sure, but two problems arise:
What are the actual rates, what is the actual cost benefit analysis of stopping adoption/step fathering, leaving kids in homes versus the benefit of allowing adoption?
The second problem is more troubling, not all homosexual couples want kids.  You are arguing against step-fathers not homosexual marriage.  The only way for you to justify this is to redefine marriage to include kids.  This is dishonest at best.  In the comments he goes on to say that he finds childless homosexuality immoral, but as he gives no justification this must come from authority, in this case religion.

Justin's central concept is to use evolution as a guide and show that living according to evolution is bad and Christian morality trumps it (non-rape vs. rape; monogamy vs. polygamy/promiscuity etc.)  However, he then argues against homosexual marriage using evolution in the opposite way:

It is a bad evolutionary strategy to take care of someone else’s children.

Can he not see the conflict in his position?

I think there is a fundamental difference of not only opinion but of morality.  Justin sees sex outside of marriage as 'ugly, and shameful', I see sex as a mutually enjoyable celebration of the freedom of two people to physically show their attraction for each other.  Justin's views on morality relate to trying to fit arguments into a pre-defined worldview based on Chritian values.  I take the view that we (almost) all have a basic morality that comes from evolution, then a social morality we learn as we grow, then (some of us) try to go beyond that using reason and logic.  This morality is defensible, can be debated and can be easily changed through logic and discussion.  It also supercedes other forms of morality, both intellectually and practically.  Justin is trying to engage this side of his morality, but keeps trying to force it to fit in with his Biblical teachings and this leads to problems in some of his arguments, e.g. using evolution as a bad thing while defending promiscuity, then using evolution as a good thing while attacking homosexuality.

The key quote is Justin's closing statement:

Rather, my goal is to directly challenge the idea that promiscuity is healthy and moral.

This argument, wrapped in a Christian flag, is justified by appealing to biology (if it happens in nature it must be unfair or wasteful) and fairness (every man should have access to a woman).

Even if I granted every one of Justin's arguments, which I don't, there are two main problems that Justin has to answer with regards to his position:

1. Serial monogamy is immoral in your world view.  There are no arguments you have made, other than a religious one, that says there could be anything wrong with serial monogamy, yet you call it immoral.
   
2. Freedom.  Who are you, or I, to say what autonomous, mentally competent, consenting adults can and can't do with each other?  If there is no harm to other individuals then a polyamorous relationship is none of your business.  If someone wishes to be celibate then that is their choice.  If someone wishes to be promiscuous then that is also their choice.

In conclusion, I would again like to thank Justin for his frank and open views and his willingness to engage in this debate.  I will not convince Justin using logic as even if I did point out flaws or inconsistencies in his worldview there is always the argument from authority to fall back on, but if I can chip away at any of the self-assurance that religion provides to people's morality then that is something.  The difference in our fundamental moral philosophy comes, I feel, from the starting point.  Justin starts from a Christian view and finds arguments that fit that view.  I start from a blank slate and try to find what is fair, what is just and what is intellectually honest.  Christianity had much to offer society in terms of morality but, like all inerrant books, people can cherry pick items to justify anything.  Christianity's day has passed, let's take what was good from it and try to build upon it, but let's also discard that which we fundamentally know as wrong: slavery, the death penalty (for misdemeanors at least), bronze age 'sexual morality' and homophobic discrimination.