KJV Only devotees think so little of the Word of God that they don't bother to investigate the modern science of Text Criticism. This science groups biblical manuscripts into families by date, geographical origin, and general reliability. Then it demonstrates when, how, and why many of the hundreds of thousands of errors crept into the text, so that the most accurate possible critical text of the Hebrew and Greek can be recovered. The results are often corroborated by the earliest church fathers and their quotations of specific texts. For example, Origin points out errors that have crept into texts that are missing in earlier manuscripts, errors that are sadly preserved in the texts used by the KJV. The most relevant of the earliest manuscripts and paypyri were of course t available to the KJV translators. This summary is almost universally accepted in both conservative and liberal seminaries.
The Hebrew and Greek texts used by the KJV translators contain many bogus verses that are missing from the earliest and most reliable manuscripts. No such bogus intrusion is more spiritually dangerous than the false ending of Mark 16:9-20. Manuscript evidence demonstrates the original Gospel ended at 16:8 and various false endings were then later added to provide stories of Resurrection appearances. One manuscript of Mark indicates that the text was invented by Aristo of Pella after 150 AD. The Greek style of 16:9-20 differs so strikingly from the rest of Mark's Gospel that its bogus nature is widely recognized by modern Bible scholars.
What makes the false ending of Mark so spiritually dangerous is its claim: "These signs shall follow them that believe...They shall pick up snakes in their hands and if they drink any deadly thing, it will not hurt them (16:18)." This cultic promise serves as the basis for the Applalachian Christian practice of putting God to the test by handing wild ratllesnakes and drinking strychnine rat poison. Many fatalities, including children, have resulted rom this cultic practice. Note that the deliberate act of picking up deadly snakes is based on Paul's accidental encounter with a viper that wraps around his hand in Acts 28:3). and the accidental treading on scorpions in Luke 10:17.