here on the free repulic it seems to me that anyone is welcome and few get banned. those that do get banned are for being obnoxious and 'stalkers' who are following certain people, for the most part. we tend to self police ourselves so banning is not required.
at dtr, there is a screening process. if the screener makes an error, the offender is bannished. it is an example of an organization that will not tolerate free speech and hegelian ideas, but as you say, it is not a free speech issue.