The church has been screwing with the Word of God for quite some time—since before Jesus, actually. If you know anything about Jesus, you know that He didn't exactly get along with the people in charge. He was constantly calling out the Pharisees and Sadducees for their false doctrine. Even as He strove to correct this, He left us with the warning that the problem of false doctrine was not over, in fact, it would only get worse. You have a few cases where people write their own texts and are clearly teaching outside of the Biblical doctrine, but in most cases they merely taint the word of God with subtlies. Over time, when such subtitles have been engrained into you and society, it becomes difficult to separate them from sound doctrine.
A personal example stems from the issue of Christmas. The first time one of my peers (a Jehovah's Witness) told me Christmas couldn't be found in the Bible, I staunchly disagreed with her. The fact that we were both young (about 12 years old) and underdeveloped in our faith, restricted her from articulating the difference between Jesus' birth and the holiday we call Christmas, which is exactly the point I was missing at that time.
These minor inconsistencies lead people to false interpretations which eventually creates 3 groups of people: those that do not study and choose to believe false doctrine (likely the people Jesus was referring to in Matthew 7:21), those who lose faith when their studies prove the false doctrines (which they believe to be true and indicative of God's Word) are false, and finally, those who are able to maintain faith by studying to find the truth.
21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. 22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? 23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
I see a lot of people spreading one-sided interpretations through the internet in an attempt to undermine God's power. Like with my friend, these conversations are usually not productive discussions, but merely accusations and selective hearing. Reading, understanding, and interpreting the Bible is like dissecting literature—it's no easy task, and it's not to be taken lightly. People neglect the fact that the Bible, though written by multiple men, is inspired by God; this means the book as a whole is a cohesive document. Topics are discussed across testaments, books, and chapters. To understand what's being said, you have to combine all the texts along with knowledge of the time period, and an understanding of the original language. Like I said, it's no easy feat.
I want to tackle some of these topics from the different angles presented and show how easy it is to lose God's voice when we don't pay attention. I don't claim to have all the answers, but as I become closer in my relationship with God, I've definitely found more clarity than I had originally. For those of you reading who have not chosen to believe in God or His Word, I encourage you to follow along anyway—I encourage you to first view the Bible as a piece of literature, connecting the story from Genesis 1:1 to Revelation 22:21, seeing how one piece connects to the others. My attempt is not to convince you of God's presence, only He can do that, but to open your eyes to alternatives you might not have considered.