Robert Rowe has gone around popularizing an argument against KJV Onlyism. While I agree with there existing tension between the Grammatical-Historical method of interpretation and KJV Onlyism. I don’t think Psalm 145 is as ironclad as Robert has presented it from my understanding. Let’s look at the argument:
12 To make known to the sons of men his mighty acts, and the glorious majesty of his kingdom.
13 Thy kingdom is an everlasting kingdom, and thy dominion endureth throughout all generations.
14 The Lord upholdeth all that fall, and raiseth up all those that be bowed down.
12 in order to make known your mighty acts to mankind
as well as the majestic splendor of your kingdom.
13 Your kingdom is an everlasting kingdom,
and your authority endures from one generation to another.
13b God is faithful about everything he says
and merciful in everything he does.
14 The Lord supports everyone who falls
and raises up those who are bowed down.
Why are the versions different? Here is a commentator to explain:
This psalm is an acrostic in which each verse begins with a letter of the Hebrew alphabet, with the exception of the nun in the MT (v. 13b). The NIV accepts the textual evidence from Qumran and several ancient versions, according to which v. 13b has been accidentally omitted from the Hebrew text but may be reconstructed from these other witnesses.
VanGemeren, Willem A.. Psalms (The Expositor’s Bible Commentary) (Kindle Locations 29591-29593). Zondervan. Kindle Edition.
This leaves it as if it seems that we have discovered the missing verse of the psalm has been found and we have it now. The issue is whether this shows an error in KJV Onlyism. I don’t think that the argument is as strong as some suppose it is. Many acrostic psalms have missing letters:
This verse numbered 13b was apparently omitted in the Hebrew text. The verse is in the Qumran manuscript, the Greek and Syriac versions, and one manuscript by Kennicott. Most modern translations include it and thereby fill out the acrostic pattern. However, missing lines in acrostic psalms is not unusual, especially in Davidic psalms such as 25, 34, and 37. See further B. Lindars, “The Structure of Psalm cxlv,” VT 29 (1979):23—30; R. Kimelman, “Psalm 145: Theme, Structure and Impact,” JBL 113 (1994):37—58; and J. Chinitz, “Psalm 145: Its Two Faces,” JBQ 24 (1996):229—32.
Allen Ross; A Commentary on the Psalms: 1-41 (Kregel Exegetical Library)(Page 909).
A KJV Onlyist may maintain consistently that this is just an instance where nun was missing. Robert Rowe should present further reasons for accepting the authenticity of the verse.