However, while other stock sites are experiencing growth...
They are? How do you know? Can you cite some verified statistics?
Many individuals have chosen to leave or become non-paying members due to their posts being consistently deleted.
Are these people unable to understand how the pretty simple TOU works? If so, they only need ask an admin in what way their deleted post violates it. They also have the option of requesting an admin review.
They must understand that unless they provide more freedom for users to combat the bashers, people will simply move on to other platforms where they can express themselves more freely.
Generally speaking, the "bashers" to which you refer provide reasons for what they say about the stock in question. As noted above, why can't others on the board--there're almost always far fewer "bashers" than enthusiastic shareholders--counter what the "basher" says with his own facts and opinions?