Because disagreement is so much more intresting than agreeing with someone. Besides most threads are formed as a question anyway, sometimes people agree and sometimes they don't. If they don't they aren't jerks or insecure they just don't agree with you. Now if a PS, PC or Xone fan would go to the official Nintendo forum to piss on Nintendo with not a single good argument that person would be a troll. Which sometimes is funny because of yhe reactions. That would probably the main reason behind it.
Please excuse my (probally) poor grammar







