You are missing the fact that most religious people aren't interested in theological discourse, much less debate.

The mere presence of debate does not preclude certainty about overarching principles. Various denominations might disagree about what's moral in a situation, but they can at least agree about why this specific kind of morality is important, and what reasoning and evidence should be relevant in the discussion, and how this morality plays into a larger conception of the Christian life. Elements like the Gospel, the Apostle's Creed, and the metaphysics of traditional deism can all be harnessed to conduct and resolve debate. There are more certainties than there are the opposite. And perfect certainty will never be achieved, even on a theological level. Since one of the charges of theology is to adapt and present Christianity to a changing world.

Unlike, say, secular moral discourse, especially manifest in political speech, which makes no effort whatsoever to establish shared principles. There are few, if any, first premises which can initiate debate. There are few agreed-upon standards for what counts as relevant evidence, or how certain values outweigh others.

Wading in secular moral philosophy, the situation becomes even more dire. No one could ever hope to walk into a secular philosophy class with modern material and achieve any guidance about how to conduct their life.

The ability to debate and resolve issues is the marker of a healthy tradition. Not all issues can be resolved. But there should at least be a vehicle to coming to the best available answer. Studying, say, the progression of Catholic theological doctrine is a good example of this. But in our post-Reformation era, in which every theological debate ends up spawning a new Protestant denomination, your lack of confidence is understandable.

I do, of course, agree with you that our broader cultural approach to such issues is entirely arbitrary and resistant to intellectual progress.

Edit: Alasdair MacIntyre's Whose Justice, Which Rationality is a stellar treatment of this problem you're noticing:

http://www.amazon.com/Whose-Justice-Rationality-Alasdair-Mac...

"anyone who divorces his wife, except for sexual immorality, makes her the victim of adultery, and anyone who marries a divorced woman commits adultery." Matthew 5:32

Combine that with God's official "Thou shalt not commit adultery"

And especially for the protestants, directly by Jesus again:

"Do not store up for yourselves treasures on earth, where moths and vermin destroy, and where thieves break in and steal." Matthew 6:19 "But store up for yourselves treasures in heaven, where moths and vermin do not destroy, and where thieves do not break in and steal."

And of course, who does this, as Jesus says:

"And if thine eye offend thee, pluck it out, and cast it from thee: it is better for thee to enter into life with one eye, rather than having two eyes to be cast into hell fire." Matthew 18:9

Now explain why you don't do what Jesus and God personally, according to the holy books, tell you to do if you get the morality from the religion.

Even if you are a believer you have to see that it's a human consensus that decides what's moral at any particular point in time. That consensus was historically at some times at some places more influenced by some holy books, therefore the witch hunt ("Thou shalt not suffer a witch to live.") and luckily it's not that much anymore, at least in Europe.

Have even more fun trying to accept the morality from Islam holy books. Note the whole Quran is claimed to be the actual "words of God.": "Whoso fighteth in the way of Allah, be he slain or be he victorious, on him We shall bestow a vast reward." Quran (4:74)

Then amongst traditionalists and others, they can't agree on whether or not classical liberal principles are compatible with Catholic doctrine or not. Christopher Ferrara and others thinks that all of United States history was a giant mistake and that we should revert to pre-Enlightenment theocracy, Tom Woods and others argue that liberalism is what Catholicism logically leads to.

No, there isn't much certainty about overarching principles. That you can't conduct your own life based on secular morality is false. Most people don't conduct their lives on any explicit morality. The ones that have ever pondered these questions in depth have always been a minority. Everyone else has only trickled down breadcrumbs from some clergyman, or ignored it.

If that's the case, then the secularist world doesn't have to come up with actual answers either. They just have to tell people what to think and do, and then they'll have the authority structure they so desired.

It sounds nice to know that when you are born, society has a place for you. They have a job for you. They can tell you what to wear, what dance to learn, and what products to buy. They can tell you how to treat your neighbor, or how to regard the Chinese. They can tell you what the good death is like.

Compare this to the paucity of experimental data to back up software development methodologies and computer language design. Most software development shops just settle on some ad-hoc worldview that works for them.

There are no out-of-the-box answers provided by anyone.

There are definitely out-of-the-box answers being hawked by someone, Whether these answers are backed up by actual theology doesn't change the fact.

By that logic, if, say people disagree about whether cryptography is good, both sides haven't been able to answer the question.