If they were the truth, they could take a site like Jwfacts and debunk it page by page and point by point. They cannot do that, so they resort to name calling, ad hominem, attacking the motive and other logical fallacies and unreasoning phobias to muddy the waters.
JWs are kept ignorant of many things, such as past teachings, flip flops, UN NGO, child abuse etc. If the WT were honest they would be more transparent. However their deception runs so deep and the rabbit hole goes down so far that everything would crumble.
For example, if they were honest about 607 vs 586 dates their whole religion would fall apart. The fundemental teaching is that Jesus returned to earth invisibly and selected drunken racist Joe Rutherford as his "faithful and wise servant" in 1919 based on the "spiritual food" he was dispensing at the time, including the "Millions now living will never die" 1925 false prophecy and the laughably arrogant and asinine "Finished Mystery" book. If you dont believe that, the whole thing crumbles and they are not "the channel". Its either true or it isnt. The preaching work and increasing numbers are not any proof, since if that was evidence the LDS church would be even more Gods channel because they have double the members in about the same time of existence, grow at a higher rate, and also preach. Doctrines do not matter to a JW although they believe in them and will argue you about them. If a QFR came out tomorrow that changed a key teaching, they would all go along and believe that too. All that matters is loyalty to the leadership of the organization. Nothing else matters.