Essan wrote, "[A] mature Christian must be in unity and full harmony with fellow believers as far as faith and knowledge are concerned. He does not advocate or insist on personal opinions or harbour private ideas when it comes to Bible understanding. Rather, he has complete confidence in the truth as it is revealed by Jehovah God through his Son, Jesus Christ, and "the faithful and discreet slave." (Watchtower, August 1st, 2001, p. 14).
Mature Christians do maintain unity and full harmony with fellow believers and are not necessarily dependent on the "the faithful and discreet slave" to maintain unity. The faithful discreet slave is an instrument to help others progress to Christian maturity. When it comes to what is stated above, it's an individual choice whether a person agrees.
If a person advocates or insists on personal opinions or harboring private ideas that are in disagreement with what the slave teaches, why is this person in association with Jehovah's Witnesses if no one can tell him/her anything? As for ex-communication, a person doesn't get disfellowshipped for having doubts, disagreeing or being disillusioned. They get disfellowshipped for taking an active stand against the organization.
it-2 p. 310 Man of Lawlessness
An expression used by the apostle Paul at 2 Thessalonians 2:2, 3 in warning of the great anti-Christian apostasy that would develop before “the day of Jehovah.” The Greek word for “apostasy” here used, a·po·sta·si′a, denotes more than a mere falling away, an indifferent sliding back. It means a defection, a revolt, a planned, deliberate rebellion. In ancient papyrus documents a·po·sta·si′a was used politically of rebels.
w92 7/1 p. 19 par. 18 Elders, Judge With Righteousness
On the other hand, when members of a judicial committee are confronted with a clear case of remorseless apostasy, willful rebellion against Jehovah’s laws, or sheer wickedness, their duty is to protect the other members of the congregation by disfellowshipping the unrepentant offender.
In all fairness, if I were to become a member of a Catholic or Baptist church, later revolt and take an active stand against their church, there might not be a formal discharge, but I'd be systematically pushed out the door.
Essan wrote, "But you certainly do not have to be "proselytizing" a different view in order to be disfellowshipped. Even seeking answers too vigorously can lead to being 'reported' and rebuked. I had a friend who used to study very deeply. He was studying the Trinity brochure and could not understand a particular sentence in it. So he kept looking for answers. He was and is a sincere JW and totally believes in the Society. He kept asking others if they understood the sentence and could explain it to him. They could not, but whereas he wanted to understand, they were content to remain ignorant but trust that the sentence must make sense, even if they didn't know how, because the Society wrote it."
Specifically, what sentence are you referring to?