"You can't trust the gospels. They're unreliable."

Many skeptics will claim that the records of Jesus' life found in the Bible are mistaken or falsified. They say that early Christians made up many of the facts of Christ's life and ministry, and that the entirety of the gospels is unreliable. But there is no proof that Matthew, Mark, Luke, and John are doctored in any way.
To display the Gospels' validity, it must first be assumed that they aren't holy books, but merely historical records.Skeptics need to treat them just as they would treat any other normal book of history, therefore eliminating any bias against Christianity. Many skeptics accept the authenticity of other historical documents, such as Gallic Wars, Jewish Wars, Annals of Imperial Rome, and uncanonized gospels, even though the were more likely to be falsified.
If the Gospels have indeed been altered, then it can be assumed that any and every other historical record has been as well. Over 5,000 manuscripts of the New Testament have been discovered, compared to other historical documents supported by only a handful. It is extremely prejudiced to say that the Gospels have been manipulated but these documents with minimal proof haven't.
Just like any other historical book, the Gospels should be considered correct until they are proven otherwise. Skeptics have no reason to question their authenticity.