as the ultimate authoriy"

You need to back that up in light of what is written in the watchtower and your "presidents"

At one point, The Watchtower Bible and Tract Society taught that God ruled the universe from somewhere in the Pleiades star system.

Charles Taze Russell, claimed that the Bible could be only understood according to his interpretations.

Rutherford predicted that the current world political order would end in 1925. And that "Millions Now Living Will Never Die",

Then you have Nathan Homer Knorr who set up a chairmanship of the Governing Body would also be affected, rotating according to alphabetical order. And finally, in December of 1975, leadership of Jehovah's Witnesses passed from the president of the Watch Tower Society to the Governing Body of Jehovah's Witnesses. This Governing Body is administrative and executive in its powers. It elucidates and promulgates the 'present understanding' of the Bible for its membership and interested persons, and clarifies its teachings by means of its publications in many languages and conventions in many countries, as it sees the need. It also appoints members to important positions of oversight. The Governing Body may be contacted by local congregations or servants to obtain advice. Members of the Governing Body also confirm everything that is written in the literature before publishing.

Then from the Watchtower….

"We all need help to understand the Bible, and we cannot find the Scriptural guidance we need outside the ‘faithful and discreet slave' organization." The Watchtower, Feb. 15, 1981.

"We should eat and digest and assimilate what is set before us, without shying away from parts of the food because it may not suit the fancy of our mental taste...We should meekly go along with the Lord's theocratic organization and wait for further clarification…" The Watchtower, February 1, 1952, pp. 79-80.

The Watchtower organization has claimed to be the prophet of God (The Watchtower, April 1, 1972, p. 197)

The Bible says in Deut. 18:20-22, "‘However, the prophet who presumes to speak in my name a word that I have not commanded him to speak or who speaks in the name of other gods, that prophet must die. And in case you should say in your heart: "How shall we know the word that Jehovah has not spoken?" When the prophet speaks in the name of Jehovah and the word does not occur or come true, that is the word that Jehovah did not speak..."

If the NWT condemns false prophesying and states that it is proof that God is not speaking through that prophet, then doesn’t this prove that the Watchtower Bible & Tract Society is not speaking for God?

The Bible plainly teaches that God is the same yesterday, today and tomorrow, and that there is an absolute truth, while the Watchtower teaches that truth changes as to what ever the new Governing body may change it to.