The official definition of a conspiracy theory (Merriam Webster definition) is "an event or set of circumstances as the result of a secret plot by usually powerful conspirators". One could add to that definition by observing the characteristics of conspiracy theories common today:
A conspiracy theory involves a general mistrust of the official or traditional account of an event.
This mistrust is usually either a priori or is based on very little evidence that is typically very selective and disparate in nature.
The conspiracy theorist often holds tightly to isolated bits and pieces of "evidence" while ignoring the "big picture".
This mistrust a priori ignores or disqualifies any and all evidence supporting the official or traditionally-held story, including those held by the scientific and academic community.
The conspiracy theorist often does not subject their "supporting evidence" to the level of scrutiny that they direct toward the official story.
It has occurred to me over the years that most skepticism of Christianity - at least the most popular kind - has an uncanny, if not identical, resemblance to your garden-variety conspiracy theory. (Again, not every skeptic is like this, but certainly the most popular ones are!) Let's take a look at these specifically:
Skeptics have a general mistrust of the official account of the life and teachings of Jesus, more specifically of his death and resurrection.
Skeptics have no academically-solid evidence to back up a claim that the Gospels are unreliable as a historical source, that the accounts of Jesus were fabricated, that Jesus didn't exist or any number of other commonly-cited objections.
Skeptics hold tightly to selective incidents and time periods where Christianity/faith was abused by those in positions of power, while ignoring the overall "big picture".
Skeptics brush aside or even disqualify all of the evidence that points to the Gospel accounts being reliable, including the entire consensus of the academic community.
Skeptics do not subject their "supporting evidence" to the same level of scrutiny that they direct at the Gospel accounts and at people of faith. Many never even take the time to research their claims at all.
In my own experience and conversations, I've noticed the following:
Many skeptics have never read any counterarguments or apologetics resources. I've run into a few who have never heard of William Lane Craig, for instance.
Some of the more vitriolic and vocal skeptics have openly admitted that they don't read Christian apologetics nor the work of scholars and historians. After all, they say, "if I don't believe God exists, why would I waste time investigating any religion?"
Skeptics come up with objections with flippancy and ease, many of which are unsound and easily answered. But instead of stopping and applying some critical thinking to those objections, they put the onus on Christians to do the thinking and researching "legwork" for them.
A good skeptic is completely justified in wanting to question Christianity. But he/she should also be skeptical of the questions and accusations against Christianity! "Question Everything" should include questioning the questions themselves to see if they are valid. I invite everyone reading this to look up the following issues for yourself:
The claim that Jesus never existed
The claim that the story of Jesus was borrowed/copied from ancient religions/mythologies
The claim that Christianity and faith has an overall negative impact on the world
The claim that faith in God is irrational and illogical
The claim that the Bible is not a reliable source of ancient history
The claim that the Bible has contradictions
The claim that science and faith are incompatible
Read the popular bloggers and authors' claims on those subjects, then read/watch a.) the actual lifelong experts in the material who have PhDs and peer-reviewed papers on the subjects and b.) the Christian apologetics resources such as William Lane Craig, Ravi Zacharias, Michael Licona, Gary Habermas and others (here is a list of those resources).
You will see precisely how much the more vocal skeptical community is willing to hold tightly to - and base their entire disbelief on - what amounts to a overarching conspiracy theory against the official story that makes up the foundation of Christianity. They do this all the while never applying critical thinking and "Question Everything" to their own views, philosophies and beliefs, and therefore they never discover how soundly evidenced Christianity is. That, my friend, is partly why I'm still a Christian today and why I'll stay a believer. I only hope that I can help others see through what is becoming a reeking cesspool of lazy, vitriolic skepticism in our world today, and by doing so convince others not throw away something of such infinite, precious value and importance.