The title of this thread is "The Error of KJV-Onlyism".
I have thought about this issue extensively and haven't been able to come up with a satisfactory answer -- until now.
KJV-Onlyism is idolatry! Rather than understanding that the KJV is just one of many English translations, the KJV-only people have elevated it to an irrational level.
Throughout the Bible, in both the Old and New Testaments, God's people are warned over and over against Idolatry. Instead of turning to God Himself, people (including God's own people) turned to physical objects made of inanimate materials, to “speak” to them for guidance, wisdom, and other matters. Idols can be made of almost any material: wood, metal, leather, paper, etc.
Rather than communicating with their true Father – the living God – for guidance and answers, people seek inanimate objects instead. They believed that those objects, rather than God, would give them answers.
Jesus specifically warned about this in John 14:6, saying “I am the way, the truth, and the life. Nobody comes to the Father except through me.” Not through an inanimate book which cannot “speak”!
Does an idol “speak” normally? Of course not! Because it is not actually a person, it speaks ABNORMALLY, and only certain people can understand what their idol is actually “saying”. (Others, of course, cannot.)