We See and Judge from our Perception.

We see and judge everything according to our own perception. 
We can never see anything as whole, in totality, at any given time. We can only look at things from a certain angle. Therefore, the wise looks from every angle and knows that no one is all good or all bad; completely righteous or completely evil. Knowing that no one is perfect, they do not pass judgment.
Remember the ancient Indian story of six blind men and the elephant?
   Here is a version in poetry form by John Godfrey Saxe.

            The six Blind Men and the Elephant

It was six men of Hindustan

To learning much inclined,

Who went to see the Elephant

Though all of them were blind,

That each by observation

Might satisfy his mind.

The First approached the Elephant,

And happening to fall

Against his broad and sturdy side,

At once began to bawl:

"God bless me! But the Elephant

Is very like a WALL!"

The Second, feeling of the tusk,

Cried, "Ho, what have we here,

So very round and smooth and sharp?

To me 'tis mighty clear

This wonder of an Elephant

Is very like a SPEAR!"

The Third approached the animal,

And happening to take

The squirming trunk within his hands,

Thus boldly up and spake:

"I see," quoth he, "the Elephant

Is very like a SNAKE!"

The Fourth reached out an eager hand, 

And felt about the knee

"What most this wondrous beast is like

Is mighty plain," quoth he:

"'Tis clear enough the Elephant

Is very like a TREE!"

The Fifth, who chanced to touch the ear,

Said: "Even the blindest man

Can tell what this resembles most;

Deny the fact who can,

This marvel of an Elephant

Is very like a FAN!"

The Sixth no sooner had begun

About the beast to grope,

Than seizing on the swinging tail

That fell within his scope,

"I see," quoth he, "the Elephant

Is very like a ROPE!"

And so these men of Hindustan

Disputed loud and long,

Each in his own opinion

Exceeding stiff and strong,

Though each was partly in the right,

And all were in the wrong!

                            By John Godfrey Saxe (1816-1887)