de facto -I have been the captain of a 'heavy' cleared to line up @ LAX -all checks and cabin secure given -due to a serious incident in the cabin we were unable to accept take off clearance,ostensibly 'blocking' the runway while the problem was resolved.Sometimes it would help to have the awareness and intelligence to understand each other's jobs;it did not stop the tower controller sending a tirade of criticism in our direction -completely unprofessional imho.It works both ways.