"Whats your opinion? Do we have collective Attention Deficit Disorder?"
Not clinically, no. However, people often call a lack of interest or desire to pay attention ADD now days. So in the modern definition (aka. pop culture definition) yes, society as a whole has ADD.
My opinion is that, for some time now, children are being taught in public schools that it's OK to be stupid. Everyone gets the same award whether they win or lose... if they're allowed to win or lose and it's not one of those places where keeping score is taboo. Curriculum's are being dumbed down to meet the lowest common denominator and what would have been considered an average student before are now in advanced placement classes. Many parents shed responsibility for raising their children and blame their kids' ignorance on the schools, which is actually partially correct as I've met some pretty stupid teachers. You'll catch more flack for correcting someone's use of their, there or they're on Facebook than if you're the one using them incorrectly.
It's never been "cool" to be smart. I get that. But when did it become OK to be average, or even below average? Why should anyone be OK with being average? Shouldn't you strive to be more? That's what my kids will be taught... not to settle for average when they're capable of so much more if they put in the effort.
As for why people on the Internet look for something to disagree with... it's the perceived anonymity that the Internet provides as described by this image:
http://tctechcrunch2011.files.wordpress.com/2009/05/shitcock.jpgI think it also speaks to the general state of mind of society. We've become pessimistic as a whole. I blame mainstream media for that. They thrive on reporting horror stories and tragedies. A good 75% of the evening news is negative, but I have to believe that there is more positive in the world than negative as we haven't yet plummeted into another world war in spite of what CNN and other mainstream media would have you believe.