#1 artificial convenience: KJV-onlyists generally tend to be Americans in the southern regions of the U.S. who can only comprehend English, and are oblivious to other languages. They would rather live with the convenience of not having to study, and ignore those who don't speak English. Ignorance is bliss.
#2 exclusivism: any other languages are simply ignored, and the KJV-onylists could care what else happens outside of CONUS
#3 'bubble' mindset: to be a KJV-onlyist, you need to place yourself in a bubble and 'ignore' all of the arguments that cannot be answered with the KJV translation, or create sub-par excuses rather than answers. You also have to be oblivious of other languages and how God reaches out to those who speak different languages! The world does not revolve around the CONUS.
#4 willful ignorance: you absolutely must show willful ignorance against textual scholarship and errors that are pointed out plainly in the translation itself. It starts to become less an issue of the Bible, but an issue of basic context and understanding of languages, instead of being so oblivious.
#5 zero desire to change: a KJV-onlyist is not interested in changing their mind, EVEN IF-- EVEN IF proven wrong. That is why [any] religion continues, because the people following it WANT to follow it, and will not change; they'll create as many lies and excuses to their conscience as it can take rather than simply say "I am wrong" or "you know what, I might consider that".
Unfortunately a lot of these rules apply to many religions and especially the problems in Christianity. However, KJV-only is one of the ultimate forms because it's something so obviously wrong, as opposed to having somewhat of a potential for contention. Another problem is that it starts to get Christians to attack Bibles and belittle those who don't use an antiquated Bible translation that was largely developed off of the Wycliffe and Douay-Rheims; retaining all mythical creatures, obsolete English, obvious manuscript errors and textual issues since it is NOT derived from a 'perfect' source. And the largest problem; KJV-only is sponsored by Satan because it mixes two very unique concepts: A) having a body of believers who are very spot-on with doctrines, i.e. salvation only through belief and nothing else, B) completely throwing the original language texts down the drain hole: which is one of Satan's goals.
Of course, repeating correct doctrines is a lot different that knowing why they are true and proving them. So KJV-onlyism does disservice to your Biblical comprehension. Sure you'll be able to tell God: "yep only believe is correct, yep pre-trib rapture is correct, yep the unforgiveable sin is never having believed in Christ paying for your sins, yep the trinity is correct, yep soul sleep is wrong"-- but when God asks you to PROVE it, you'll be standing there with nothing.