Originally an amusing and unique handle for chat rooms and games (originally MINE that is) which has become a comical (and increasingly widespread) way to 'poke' fun at evildoers, trolls
or any one of life's petty annoyances within newsgroups, chat rooms and blogs.
It's main purpose is to dismiss annoying arguments, people and situations in a civilized manner without resorting to flaming, net hooliganism or other kinds of embarrassing behaviour.
A way of saying "this little thing will not get me down".
The use of the "Fork Of Justice" ranges from literally using a fork to poke the offending party (in chat), posting a picture of a fork in a thread or blog, or as a comical over-played super hero roleplay.