Quoting Mantey, Bowman, Rhodes is not the solution in search of truth. These guys do quite a bit of twisting quotes themselves. They are not reliable sources. The WT is no saint either. Both parties are right sometimes and wrong other times. Evangelical sources attacking the WT are way off at times that it is surprising there are plenty of takers out there.
The McKenzie quote by the WT in my opinion is fair use. McKenzie was clear with the statement the WT quoted. That he is a Trinitarian, and doesn't agree with the WT interpretation overall is besides the point. Mckenzie is not that all clear on various trinitarian texts to have Rhodes quote it for full support.
Harner too presents a picture somewhere between the WT position and traditionalist views. Actually, Harner says or implies that the traditional translation "the Word was God" is a no-no. The part the WT quoted was done correctly -- to indicate that the predicate of Jn 1.1c is not definite. And I ask, what is the opposite of "definite"?
What about Baptist Mantey? Mantey's letter is more of an embarrasment to his scholarship (his Greek grammar is a favorite of mine) by revealing he let his emotions do the talking in respect to the WT. His letter was not articulately done, not to mention obvious exegetical mistakes within, which even other scholars would dispute.