"Deconstruction," for most Christians who claim to be going through such a thing, almost always starts with an interaction with the message of the world - something the world says that someone then takes as true because the world says of course it is true and it must be true - that then calls into question, in some way, the message of faith.
It started, and it often comes back to, something called "science." At least, such is true in our lifetime. (There have been other "wisdoms" raised from the very beginnings of the faith.) So let's talk about science.
Science makes claims like, "the universe is billions of years old." They do this in a few ways - by calculating very rough speeds from very far distances based on very specific algorithms that they've had to adjust multiple times over the course of developing them to arrive at where they currently are, and underlying this is a lot of assumption - assumption, for example, that things have either always been traveling at the rate they are traveling now or that they have always been slowing at a rate they are slowing now (and therefore, were once moving much faster, a rate we can also calculate with some kind of algorithm). There's nothing at all to say that any of this is true, but the world says that it is true, and if you ask questions, it's because you "don't believe in science."
But we know the way that planets in our own solar system orbit, how they both rotate and revolve around their various paths. We know that some things wobble. What if some things wobble more than others? What if the amount of distance traveled during a wobble is greater in some cases than others? What if our lifetimes are so short (and our knowledge of space, thus far, so limited) that what we're seeing is a wobble and not a movement, and we just haven't seen it wobble back the other way yet? Science can't answer these questions; they can just call you stupid for asking.
The same is true about carbon dating. The earth, too, science claims, must be billions of years old. We know this because of the way that carbon acts, so by using the carbon, we can figure out how old things are. But we only know how carbon acts in the environments that we've tested it in, and science itself claims that the earth has gone through different eras and eons and scientific stages and changes. What if we're wrong about how carbon acted during an ice age - which science tells us have existed? Then all of our carbon dating is wrong because we have no way of knowing how carbon actually acted in the environment in which it existed.
This is why global warming is a problem. Science tells us the earth has gone through periods of coolness and warmness and that we're now entering another period of warmness, but that this one is "unprecedented." This one is caused by our own human activity. How do we know? What caused the other periods of weather change? Science won't say.
Then "science" goes on to make claims about human nature, human development, evolution, homosexuality, disability, and so on, and it tells us that our Bible is just not compatible with these things. It tells us these things are true, and whatever claim we want to make on faith has to account for these scientific "facts" or we are blind, naive, stupid, backward, and uneducated. We're "uncultured."
Well, nobody wants to be uncultured or stupid, so even those in the church start saying that these things are our starting point - this "science" is the set of facts that we must deal with, then we start changing the faith to meet them. Changing things like our understanding of the creation of the world or of the dignity of human beings or God's intent for man. We start to say that our Bible doesn't really mean what it says here or here or here, and that makes it easier to say that it doesn't mean what it says there, either, and all of a sudden, we're left with a faith that we're trying to build on the basis of "science" instead of fitting the science to our faith.
Remember, friends - science has changed a ton even over a relatively short period of human history. It wasn't that long ago that humans believed the earth was flat or that the sun revolved around the earth. It wasn't that long ago that we believed HIV was a curse brought on active homosexuals for their sin or that red-headed children were more likely to be possessed. And yet, "science" wants to stand in front of us and claim that it is the authority for truth? Even while it confesses that it continues to change and grow and develop?
And we believe that? We believe that so much that we're willing to throw away thousands upon thousands upon thousands of years of consistency in what God has said from the very beginning, all of which, by the way, has been shown to be true over and over and over again.
But this is how it starts....
(For the record, I believe that faith and science are not necessarily at odds with one another, that there are ways to harmonize them that doesn't require compromising either, but requires us to be fully honest about both.)