You cannot fully describe a glass.
Go ahead, try it!
You can describe how it looks, how it feels. You can, at least theoretically, describe its history, who created it and when, who drank from it. You can describe its length, width, height, temperature, refraction rate, transparency, and a gazillion other factors.
And yet, you haven't fully described it. You cannot describe every last atom in it, along with its exact path through time and space. And even if you could - if you excuse, for a moment, the little dabbling in quantum mechanics here - as it seems, it might not only be practically impossible to describe a thing to its end, but also hypothetically impossible at the most fundamental level of the universe.
And yet, we somehow manage to think that, once we have labelled a person as retarded, evil, antisocial, a religious fanatic or an atheist amoral pig, or whatever other label you like to associate with your resentment - that this, then, should be enough to never, ever have to waste another thought on that one person again.
In short, we're all pathetic little hypocrites. And now, after we've meditated that for a while and got duly depressed, let's start laughing about it, and take it easy.