A couple things.
There is no appears in suppoters posts being wiped out. Its fact. A spade is a spade.
Second thing, you do not have free speech rights on a message board. When you sign up you have to agree to the terms of service to use the service. This curtails your right to free speech, but its not really speech its a message board. If you want free speech write a book about what you want and publish it, or start your own board or club or group or go stand on a soap box. That is your right of free speech. when you sign up you basically are agreeing to a contract in which you agree to have speech moderated and regulated waiving said rights. Its also like when you join a company or an organization and sign those clauses where you can be fired for saying or doing things embarrassing to the company, whine in truth you have the freedom to do what you want or say what you want, the company has a right to regulate how it is represented. Same concept here.