Let me answer that two ways. First there is no problem with any bible that helps you find God, lifts one up spiritually or provides hope in times of trial. Now secondly, if one is looking to do theological research in a scholarly fashion then I'll allow a biblical scholar to answer you.
The problem with the KJV is basically that it is an okay translation of a bad text. By “bad text,” I mean that when the KJV translators worked, they had very few Greek and Hebrew manuscripts to work with, and most of them were late. Since then (1611), scholars have made a tremendous effort to uncover older, more reliable manuscripts that have been hidden in monasteries all over Europe and the Near East. Great progress was made in the 19th and 20th centuries, and we now have several thousand manuscripts of the New Testament alone (the KJV translators had a mere handful). All these manuscripts have been carefully compared with one another and, through a process known as “textual criticism,” scholars have determined which are the more reliable texts and reconstructed as closely as possible what the biblical writers originally wrote.
The “Antiochene” texts the person refers to are typically called “Syrian” or most often “the textus receptus” (Latin for “received text”). They are in fact the LEAST reliable manuscripts (my emphasis). They are relatively young text (from the 12th and 13th centuries) that are many copies removed from the originals. The scribal tradition tended to keep errors that had crept in in the course of copying the text, so the Antiochene texts have all these accumulated errors. The Alexandrian texts are older and more reliable (dating from around the 4th century). All modern translations (like the NRSV and NAB) draw on all the texts and make informed decisions about which manuscripts are most reliable for a given passage. They thereby represent more closely than the KJV what the biblical writers actually wrote.
The Dead Sea Scrolls (DSS) prove absolutely nothing about the KJV (my emphasis). The DSS include manuscripts of the Hebrew OT that are much older than any we had before. They are important in reconstructing the original text of the OT. Some of the ancient DSS texts correspond well with the medieval texts that have long been known, but others are quite different. As with the New Testament, scholars have to compare all the available texts to determine what version is most original. But all this text critical work precedes translation, so these scrolls have no direct bearing on the KJV.
Basically, your correspondent wants to use the KJV as the authoritative English version of the Bible. It is not. It is just a translation made by a committee of scholars working for King James in 1611. They had limited access to the original texts and limited knowledge of the biblical languages (especially Hebrew). In the past four hundred years, we have found many more manuscripts and learned a great deal more about the languages. Anyone wanting a good representation of what the biblical writers wrote should steer clear of the KJV (my emphasis). I constantly strive against unreasonable attachment to the KJV when I teach the Old Testament.
By the way, the KJV translation of the New Testament sometimes has absolutely no basis in the ancient texts (my emphasis). For example, Paul’s question in Acts 9:1 is taken from the Latin Vulgate version, but occurs in no Greek text. Both Mark 10:17 and Luke 18:18 were modified to agree with Matthew 19:17 without manuscript support. The KJV translated the “long ending” of Mark, even though the “short ending” is clearly the more original (see the NAB for both versions; the KJV translators had no way of knowing about this since they only had only late manuscripts).
