Christians can believe whatever they wish so this is not about an attitude to "others". Each one must give account directly to God and Christ, not other Christians. This is the attitude to OTHER BIBLE PERVERSIONS that is perfectly valid. If you had ten bottles labeled as "TONICS" but nine of them actually contained various levels of poison, it would be your duty to let people know that they are not all tonics.
What could be more historically verifiable than the fact that for over 300 years there was ONLY ONE ENGLISH BIBLE throughout the English-speaking world which was in general use? Kindly go to Bible Hub and check out all the 30+ commentaries. They were all based on the King James Bible. So all these commentators belonged to a "cult" according to some of you.
By this silly logic it would be plausible to claim that motor vehicles are of the devil...
After all, we had horses, oxen, etc, and animal-drawn transport for more than twenty centuries, why do we need the internal combustion engine and motor vehicles??!?
Obviously this is just nonsense, but, so then, is your argument...
And the RCC used a very similar argument for centuries to deny anyone access to a Bible in a language other than Latin.
(This was backed by executions...)
But then, guess what, the REFORMATION happened and Bibles in many different languages appeared.
But, by your logic, all of them, except the KJV, are all demonic trash!
Also you seem to have no idea that there were several English translations that were published both before and after the arrival of the KJV. All of them had substantial use and most of those translations are still available today.
But lets say for the sake of argument that for 300 years no English-speaking Christian read or used any other Bible apart from the KJV, this in no way, by itself, proves that it was a good translation, or even the best for that matter. And, ally that with the fact that until the 20th century the various Churches still had considerable influence in making decisions for their adherents about what translation was acceptable. In addition, particularly in Europe, even in the post-Reformation period the rank-and-file did not own their own Bibles even if they could read, in which case what they read was stacked in the pew next to the hymn book. That kind of subtle coercion makes the claim even less tenable. It just meant people read and used what was available, not that it had any particular virtues...
It is a massive stretch to try and make the argument that the KJV is the only valid translation, or even the only valid English translation, when, really, the only apparent "evidence" that is presented is the rather obvious fact that when comparing the KJV to other translations that they are "different"
And, as far as I am aware, not one the KJVO adherents active on this forum have the slightest training in the original languages, never mind any real knowledge of manuscripts and which are the most accurate and reliable, and so have no idea which, if any, of the translations are correct, yet are willing, month in and month out, year in and year out, to argue the toss about a topic that they know absolutely nothing about!
Go figure...