As a Lutheran, I have the advantage of being able to thank the person for using a Lutheran-inspired document. About 80% of the translation is taken directly from the Tyndale translation, which is based on the third edition of the Textus Receptus. Luther based his translation on the second edition and Tyndale was a disciple of Luther.
There is no need to refute this position. The arguer is reading the Bible. The KJV agrees with the other major translations about 97% of the time. Instead, it is a chance to celebrate our points of agreement. A friend uses the KJV because he is at ease with the language, which is noted for its poetry and beauty. These are things to be celebrated. The arguments about the deuterocanon and textual backgrounds can be saved for a day when you have a closer relationship.
If this is hard to swallow, think of it this way. His understanding of the world and his place in it could come from reading People magazine instead. Not so bad now, is it?