It  is irrelevant  whether the  message in  question violates  acceptable
network policy (or rather, it would  only make the poster's case worse if
it did). The  list you are running  is a subset of  the private computing
resources of  your (or some  other) university which said  university has
not agreed  to make  available through any  generic agreement  with CREN,
EARN, or whatever. That is, unlike  the forwarding of RSCS files which is
a sine qua non condition for joining CREN, it is up to your university to
decide whether to  make these resources available to the  list at all and
how they should be used in the  best interest of the university. You have
been appointed list owner by the staff  of said university and it is thus
your responsibility to  decide whether a particular  category of messages
is appropriate for the list. If the  subscribers do not like it, they are
free to leave,  or to use "better"  forums such as usenet  to argue about
the relationship between the first amendment and electronic forums.
 
Personally, if I had been accused  of racism after reminding a subscriber
that one  of his postings  violated the guidelines  for my list,  I would
consider sending a copy of the whole exchange to his system administrator
(depending on how  it happened). Some people are apparently  out here for
the sole  purpose of  disrupting mailing  lists which  used to  work just
fine, and there is no reason to put up with them.
 
  Eric