The internet is a faceless medium. Being detached from your persona and being able to create a new one is quite the lure for most people. If they are overly nice in the real world, then perhaps they wish to vent like an idiot on the net. Some people retain their face and often just be themselves. It all depends on who you are talking to and how the consider the internet.
Some of you may treat this place like another forum to dump your ideas into. Others may treat it like a home, where they cultivate relationships and discuss ideas in a way that they would not be able to in a real-world environment. So pertaining to the original idea, I believe that it depends on what the person coming to the internet is seeking. A place to vent their pent up frustration? Douchebag. A place to communicate with others in a manner where they might just be read by a stranger with common interests and beliefs? Normal poster.
Of course, one can get absorbed in such a world, dedicated hours and hours of their time to posting and replying, conversing and clicking. This isn't so good, and will probably lead to long sleepless nights of watching your monitor. For some, like me, this isn't so hard. When your work involves staring at that screen regardless, it's no different to come home and do this. Hmm...
tl;dr? Douchebag = douchebag or normal person who wants to release.