The truth is that Christianity has many conflicting beliefs that contradict one another, such as conditional salvation vs. unconditional salvation, the proper baptism (sprinkled with water vs. fully immersed), female pastors, and the "end-times" (the rapture, pre-tribulation, mid-tribulation, and post-tribulation).
It's obvious that Christians aren't united, and they never have been. The majority of them have the perpetual habit of accusing other Christians of not being "true Christians," and this accusation is as old as Christianity itself (read
1 Corinthians 1:10–17). The problem I have with Christians accusing other Christians of not being true followers of Jesus is that they can never agree on what the Bible truly says, and they constantly argue, insult, and fight one another about what they believe the Bible teaches. The truth is that if you ask the same theological question to a broad group of Christians, you will receive very different answers. All of these Christians will cite the Bible in an attempt to defend their answers, even though their answers are very different and contradictory.
It is also worth noting that they don't agree on whether salvation in Jesus Christ is unconditional or not, although they all read the Bible. Some Christians claim that a person's salvation is conditional, and they would quote a few scriptures they believed supported their belief. Some Christians claim that a person's salvation is unconditional, and they would quote a few scriptures they believed supported their belief. Yet other Christians claim that baptism or speaking in tongues is required for salvation, and they would quote a few scriptures they believed supported their belief. They contradict each other.
Questions about how to properly baptize believers (fully immersed in water or sprinkled with water), whether it is biblical for women to be pastors, and about the alleged end times (pre-tribulation, mid-tribulation, post-tribulation, and the rapture of Christians) would elicit the same kind of derision among Christians. Not to mention the churches staking their claim as the "true church" and implying that Christians in other churches are wrong in their theology and biblical interpretation. They even argue about whether Jesus' mother remained a virgin after giving birth to him or if she had other children after him.
The truth is that Christians are very divided, intentionally separate themselves into different churches, and adhere to different doctrines and scriptural interpretations, which have occurred in both historical and contemporary Christianity. Catholics and Protestants have different church doctrines, dogmas, and interpretations of the Bible. So do Mormons (LDS), Jehovah's Witnesses, Messianic Jews, and Orthodox Christians, which include Eastern Orthodox, Oriental Orthodox, Ethiopian Orthodox, and Greek Orthodox. Also, there are Baptists (First Baptist, Second Baptist, Southern Baptist, Reformed Baptist, Primitive Baptist, Anabaptist, Freewill Baptist,
and others), Methodists, Mennonites, Seventh-day Adventists, Assemblies of God, Apostolic Church, Quakers, Pentecostals, Church of God, and many other various churches that aren't on the list. In fact, the precise number of Christian denominations is debatable.
Ironically, they all believe that they are correct about their beliefs and everyone else (including other Christians) is wrong about theirs, but then they have the audacity to claim that the Bible is the word of God and Christianity is the only true religion in the world. In my opinion, there's no reason to believe any of them. I think it's unreasonable for any Christian to claim that their biblical interpretation and theology are correct while insisting that other Christians are wrong, that the Bible is divinely inspired, and that Christianity is the only true religion in the world. It is also irrational, in my opinion, that Christians seem to expect non-Christians to accept the Bible as divinely inspired and the final authority on moral issues, yet they can't agree on what the Bible says.