I'm not completely with it. Kishi has a point here and in compare with other manga's it's a strong one but the reality itself is kind of fact, the thing that differs is our point of views. For example there is a light but people from down stairs see it red and people from up stairs see it yellow. One may get confused about the color but the fact is that there is a light and it's not important how you look at it. It's the same in a gray world, when you don't have a straight guideline and you should decide with your own senses, what's right and what's wrong gets lost in the mist of our lack of knowledge. But when you have strict instructions for your life, world gets clear in front of your eyes while the other who don't believe in your beliefs get in your way an yet you should fight them back with tearful eyes because you know you all have almost same goals but they won't understand you and leave you no way but fighting back. Here is were Itachi's image of reality shatters. He is a man who can see the world from the skies, like a hawk looking down at the forest. The he sees how those in the forest get lost despite of their determination and as he doesn't have a better way to proceed, he loses his believe in everyone's beliefs.
