Medical conditions?  Mental health issues?  Then the public needs to be aware of that as well.  If this person has such overwhelming mental / physical conditions that his own safety as well as the safety of others is put at risk, then its the public's right to know as well as the airline's.  

Consider that this person could have been severely injured by fellow passengers who viewed his behavior as a viable threat to their safety.  Its not fair to them for being forced to use extreme efforts to restrain the person (and potentially facing lawsuits for wrongful(?) death, had this (or any) individual been violent.   

So- the heck with a blanket closed hearing.  We all have a right to know.  The judge can then decide what information is deemed private.