Without even addressing the veracity of what you wrote, it is to be admitted that the NIV has some faults, as do all bible translations. The KJV certainly has more than most modern versions. It must be understood that we have none of the originial autographs of bible writings. All that we have are copies. When dealing with copies, textual criticism is the means by which we determine what is most likely the originial writings. Textual criticism has been developed over time and is the recommended standard of all reputable scholars.
Jesus said that His words would not pass away. God has provided providentially many means of preserving His word throughout the centuries. As humans, we are expected to use every means at our disposal to determine the originial writings, including reasoning and sound logic.
In the early 1900's, it was recognized that a revision of the KJV might be needed. This was because earlier manuscripts, (Vatican and Sinaitic among them) that would be more accurate do to their closer date to the originals, and the fact that many of the words used in the KJV were obsolete, or had changed meaning over the centuries. Also, the study of the ancient Greek and Hebrew languages was in it's infancy at the time of the writing of the KJV. Studies in these languages have added much to our understanding of the bible. A committee of eminent scholars, from every denomination was set up for this task. It included such scholars as B.F. Wescott, F.J.A. Hort, J.B. Lightfoot, R.C Trench, and A.B. Davidson. The American scholars included Phillip Schaff, J.H. Thayer, and William Henry Green. These committees included such diverse men to keep individual bias out of the translation.
The American Standard Version followed, to give the language more of an American flavor, and take some of the stuffiness out of the English version, which as Charles H. Spurgeon said was "strong in Greek, but weak in English". The American ASV included in it's committee the above American scholars. Following this came the RSV, which included on it's committee such well known scholars as Edgar Goodspeed, and James Moffatt.
The question becomes do we accept the findings of textual criticism, a tool which is indispensible in translating a correct bible, or do we just accept the copies without any effort to determine their accuracy? Do we accept the findings of eminent scholars, who are experts in the original languages, and have spent their lives devoted to finding the truth and in developing techniques to determine that truth? Or do we accept the findings of those, who while not experts and knowing only a small fraction of what the scholars listed above know, are absolutely sure, based on their own personal bias, that the KJV is the most correct version?
For me, it is a slam dunk.