Just a quibble. There are only three passages contained in the new testament that all scholars of all persuasions are quite certain were not in the original documents. The prostitute being stoned and the above statement are one of those passages. It was added by a Catholic monk hundreds of years after the new testament was written. If you check the footnotes to your bible near that passage, you will probabably find a notation to that effect.
What about Romans 3:23 - "ALL have sinned and fall short of the glory of God"? Makes the same point, doesn't it?
That's why I called it a "quibble." The passage is not theologically unsound. It just wasn't in the source documents.