There are a LOT of things wrong with Christianity as a religion. Its history, its holy book, the kind of person it molds you to become, the fact that it’s still strongly socialized in many children, the political dogmas it has sprouted in the Western world, and so on. It is important to talk about all of these things.
However, none of these things are necessarily fundamental to the religion. All ideologies or worldviews have a core, a set of fundamental premises which must be true in order for that ideology or worldview to make sense. In some cases, these premises are explicitly stated, and in other cases, you have to infer them. Even if they are explicitly stated, you must still verify their fundamental nature: sometimes a group will have a strong incentive to lie about its fundamental premises (for example, cult idelogies), and sometimes followers who state core premises may simply be mistaken (for example, the people who try to reduce religion to love or peace, when these things have little to do with the core of religious worldviews).
Buddhism is one example of a religion which has explicitly and clearly stated its core premises: the Four Noble Truths. If you believe that the Four Noble Truths are invalid in some substantial way, then you couldn’t be a consistent Buddhist, because everything is (in theory, anyway) derived from them or supported by them. You may believe in the Four Noble Truths and not be a Buddhist. You may also not believe in the Four Noble Truths and claim to be a Buddhist, although you would be dishonest in doing so. If the Four Noble Truths are true, this does not thereby prove that all of Buddhism is true. But if the Four Noble Truths are false, then this definitely would prove that Buddhism is invalid as a worldview (this, of course, does not imply that every single part of Buddhism must be invalid).
What are the fundamental premises of Christianity? There is no explicit list of such premises. However, we know how a Christian is defined by Christians: a person who believes in Jesus as their savior. What premises does this imply?
1. There is a god that created the universe.
2. This god sent its son, Jesus, to be sacrificed in order to make our salvation possible.
3. We must worship this god and its son as the way to salvation.
I have problems with premises 1 and 3, but these problems are frequently discussed in arguments and debates. What is seldom discussion are the implications of premise 2. This process is called atonement, and there are many opinions about what it really means, many disagreements, even though they are all supposedly based on the Bible. No surprises there, as Christians agree on very little, while spending a lot of ink (or electrons) quoting Bible verses for their side. But the proposition that no one disagrees about is that Jesus was sent by God to be sacrificed in order to make our salvation possible. How this actually works in relation to God, humans, and Jesus, who’s forgiving who and why, is of no further relevance and only serves to keep theologians employed.
That, I contend, is the most evil principle ever proposed by any religion. Not because of its consequences (telling people to kill heretics, for example, would bring about a great deal more destruction), but because it represents a complete negation of justice in the purest form ever devised. Nothing else that I know comes close to it.
If justice means anything, it is the assignment of responsibility for actions, and the rational and just evaluation of a person based on that responsibility. You are responsible for events in the world based on the actions you commit, and you are responsible for that part of events which you caused by your actions. To give just one simple example, if you run a pedestrian over, and they die later of their wounds, you are responsible for the death to the extent of the medical consequences of you running them over.
The principle of atonement is the exact opposite of justice, in that it posits that the sacrifice of one person atones for other people’s responsibility. This is the equivalent of, in our example, killing the judge’s child in order to atone for running the pedestrian over. It is a principle which, if implemented to any degree, would lead to nothing but pure evil. It is a principle which runs contrary to all notions of fairness and empathy that are inborn in the human organism, notions which Christians profess were crafted by God, but which contradict this unjust principle.
Christians generally act as if convincing atheists of principle 1 is sufficient to turn them into Christians. In practice, this may be so, but logically it cannot be so. One can accept principle 1 and still reject principles 2 and 3. And in my opinion, anyone who is an ethical person to any degree must reject principles 2 and 3, otherwise they are being inconsistent. People who claim to have been atheists and having been converted by some argument or other must either be evil or ignorant of what they converted to. The latter is most likely. Unfortunately, too many debates and arguments about Christianity revolve solely around whether God exists, creating the illusion that accepting the existence of God must mean accepting Christianity as a worldview.
In order to prove that we should adopt the Christian worldview, Christians must demonstrate, not only the existence of God (an impossible task, as almost 2000 years of apologetics has demonstrated), but also:
* that delegating responsibility of one person’s actions upon another person, and punishing that other person, is just;
* that worshipping a being which created evil, and brought about this evil sacrifice, is a good thing.
These two other hurdles do not follow from the first. Even if one could prove that God exists, this would not prove that justice is exactly the opposite of what it is, or that one should worship such a being in view of all the evils of the world. If God exists, but is pure evil, then the correct, sane response would be to opposite it with all our energies, not worship it. To say otherwise is nothing more than might makes right rhetoric.
Of course, Christians already have a strong incentive in worshipping God: that’s what their in-group does. They also have a strong incentive to accept the injustice of the Jesus narrative: they believe that they benefit from it, by being saved. Of course they are incorrect about the latter, since God does not exist and therefore there is no salvation to be found in Christianity. But even if God did exist, it would still be an irrational proposition: why should anyone trust an evil god about its claims of salvation? I suppose we could call this Chamberlaining (in reference to Neville Chamberlain trying to appease Hitler).
The basic fact is that, if God exists, then all bets are off. This is exactly the flaw that they project upon atheists (“If god does not exist, everything is permitted”). It is Christians who believe that salvation delivers us from sin, even the sins they commit during this life. If Christianity is true, then everything is permitted. Christians try to get around this by saying that anyone who loves God will obey God, but that makes no sense. We don’t obey people because we love them. We obey people because we fear them. And that is what Christianity is really about: fear, fear of sin, fear of impurity, fear of “the world,” fear of disapproval from one’s fellows, fear of being “unsaved,” fear of Hell.
The denial of justice at its most basic level opens the door to treat God as a moral absolute. If there is no justice, then you can’t object to God’s orders being automatically good. You can no longer object to genocide, mass enslavement, mass rape, familial murder, cold-blooded executions. And that’s the corruption of the human sense of morality that Christianity does.
Of course, Christians believe that they are moral people. No one seriously believes (apart from some mentally disturbed individuals) that they are evil people. But Christians are stealing the concept of justice from secular worldviews. Which brings me to another popular apologetics projection, especially on the Internet: presuppositionalism. Presuppositionalists propose that secular people “borrow” a number of concepts from the Christian worldview, that logic, morality and the uniformity of nature can only make sense if God exists.
But this is exactly backwards. It is the Christians who have no grounds for logic, morality and the uniformity of nature. There is no logic, morality, or uniformity of nature possible if God exists, because everything goes if God exists. God could make it so that logic no longer applies, that something immoral becomes moral (like genocide), and miracles are by their very definition a break in the uniformity of nature. Christians only believe in justice because they borrow it from secular worldview, because there is no such thing in Christian doctrines. Christian doctrines give us no objective standards about what makes an action good or evil, only God’s will, which is a subjective construct. If genocide can be both right and wrong within the same worldview, then it is absolutely useless.