WSEV12: The short answer is that as long as you are not baptized, you are allowed to have your own views. After you are baptized, you are expected to keep dissenting views more or less to yourself, and you can only talk about them in a limited way. Many here have been kicked out and lost contact to family and friends simply because they had a different oppinion.
Here is an excerpt from a trial some years back where one of their leaders discuss the importance of unity in belief:
Q. Is it not vital to speak the truth on religious matters?
A. It certainly is.
Q. Is there in your view room in a religion for a change of interpretation of Holy Writ from time to time?
A. There is every reason for a change in interpretation as we view it, of the Bible. Our view becomes more clear as we see the prophesy fulfilled by time.
Q. You have promulgated -- forgive the word -- false prophesy?
A. We have -- I do not think we have promulgated false prophesy, there have been statements that were erroneous, that is the way I put it, and mistaken.
Q. Is it a most vital consideration in the present situation of the world to know if the prophesy can be interpreted into terms of fact, when Christ's Second Coming was?
A. That is true, and we have always striven to see that we have the truth before we utter it. We go on the very best information we have but we cannot wait until we get perfect, because if we wait until we get perfect we would never be able to speak.
Q. Let us follow that up just a little. It was promulgated as a matter which must be believed by all members of Jehovah's Witnesses that the Lord's Second Coming took place in 1874?
A. I am not familiar with that. You are speaking on a matter that I know nothing of.
Q. You heard Mr. Franz's evidence?
A. I heard Mr. Franz testify, but I am not familiar with what he said on that, I mean the subject matter of what he was talking about, so I cannot answer any more than you can, having heard what he said.
Q. Leave me out of it?
A. That is the source of my information, what I have heard in court.
Q. You have studied the literature of your movement?
A. Yes, but not all of it. I have not studied the seven volumes of "Studies in the Scriptures," and I have not studied this matter that you are mentioning now of 1874. I am not at all familiar with that.
Q. Assume from me that it was promulgated as authoritative by the Society that Christ's Second Coming was in 1874?
A. Taking that assumption as a fact, it is a hypothetical statement.
Q. That was the publication of false prophesy?
A. That was the publication of a false prophesy, it was a false statement or an erronious statement in fulfilment of a prophesy that was false or erroneous.
Q. And that had to be believed by the whole of Jehovah's Witnesses?
A. Yes, because you must understand we must have unity, we cannot have disunity with a lot of people going every way, an army is supposed to march in step.
Q. You do not believe in the worldly armies, do you?
A. We believe in the Christian Army of God.
Q. Do you believe in the worldly armies?
A. We have nothing to say about that, we do not preach against them, we merely say that the worldly armies, like the nations of the world today, are a part of Satan's Organization, and we do not take part in them, but we do not say the nations cannot have their armies, we do not preach against warfare, we are merely claiming our exemption from it, that is all.
Q. Back to the point now. A false prophesy was promulgated?
A. I agree that.
Q. It had to be accepted by Jehovah's Witnesses?
A. That is correct.
Q. If a member of Jehovah's Witnesses took the view himself that that prophesy was wrong and said so he would be disfellowshipped?
A.Yes, if he said so and kept persisting in creating trouble, because if the whole organisation believes one thing, even though it be erronious and somebody else starts on his own trying to put his ideas across then there is disunity and trouble, there cannot be harmony, there cannot be marching. When a change comes it should come from the proper source, the head of the organisation, the governing body, not from the bottom upwards, because everybody would have ideas, and the organisation would disintegrate and go in a thousand different directions. Our purpose is to have unity.
Q. Unity at all costs?
A. Unity at all costs, because we believe and are sure that Jehovah God is using our organisation, the governing body of our organisation to direct it, even though mistakes are made from time to time.
Q. And unity based upon an enforced acceptance of false prophecy?
A. That is conceded to be true.
Q. And the person who expressed his view, as you say, that it was wrong, and was disfellowshipped, would be in breach of the Covenant, if he was baptized?
A. That is correct.
Q. And as you said yesterday expressly, would be worthy of death?
A. I think - - -
Q. Would you say yes or no?
A. I will answer yes, unhesitatingly.
Q. Do you call that religion?
A. It certainly is.
Q. Do you call it Christianity?
A. I certainly do.
You can also see how the Watchtower answer questions form its own members in various correspondences with the watchtower:
you can make up your own mind as to how interested they are in an actual dialogue, and how much they just want the members to agree with them.
On a personal note, i can add that my girlfriend lost all her "active" friends the moment she began to show a lack of interest in what they was teaching.