All you have to do is go to a Watchtower study to see independent thinking isn't allowed. At the WT study they ask you a question and you underline and repeat the answer they want to hear. Not exactly a free exchange of ideas.
I'm sure most of us can remember a new person, probably a study coming to the WT study and making a comment outside of the information given in the paragraph. They were gently informed that expressing your own ideas wasn't what the WT study was about.