When we stand close to a big painting, we can only focus on a small part of it. Every single person we see is a big painting and our encounter with each one of them is like us standing close to the painting. We only see a part of the person, not the whole.
To draw any conclusion about the painting from the small part we see would be an unjust view of the whole picture. But so many of us are ready to make that jump without taking into consideration the possibility that there may be more than meets our eyes.
All we need to do is take a step back, and see the bigger picture.