Next to the tips others have already given, it *might* also be a reasonable idear to add your attacker to your trustlist, preceded with a "~". At this moment, while you both are new to the forum, this doesn't matter the slightest bit... But rejecting him/her from your trustlist will make sure that you indicate to the forum that you don't trust any ratings left by this individual, and you would not like to see him end up in DT. It's a longshot that this will ever happen, and if it does it's defenately not sure that your rejection will prevent him from ending up in DT, but i'd still do this out of principle.... Just in case.
Only do this if you don't trust the ratings left by your troll tough
So, in your case, go to
"profile" => "Trust" => "Trust settings"
Add
~Trollname
in the form, and click on "update".