You may wish to check the definition of "harassment" (
http://www.cps.gov.uk/legal/s_to_u/stalking_and_harassment/#a02a) You
can see here that the Crown Prosecution Service defines harassment as
"causing alarm or distress" as well as the more traditional "putting
people
in fear of violence" depending on which law is being applied. As such the
use of the term "harassment" in its strictest use does not legally mean an
incitement of violence.
Please note the usual: I am not a lawyer, please seek legal advice before
taking any actions or inactions based upon this information etc...
Putting my professional hat on for a moment...
"Alarm and distress" can be interpreted very broadly with respect to the
internet. Especially if you can tie it up to privacy laws.
We had one case a few years ago where an individual was disclosing RL names
& addresses of people on a social dating website; definitely not the same
sort of thing (as there is an obvious risk factor in that context), but
they prosecuted him largely for the privacy issues than the actual risk of
harm.
With all that said; we should be careful using the term "harassment" too
much (especially off-wiki) because, as Edward says, if not accurate or
reasonable then it is libellous.
Tom