The best way to demonstrate how Chaucer never passes judgement of any of his characters is to pull lines from the text showcasing this element. An excellent way to accomplish this might be to focus on the characters who are amoral or not pleasant people because that would best show Chaucer's graciousness towards them.
Take the Friar for instance. The Friar is a complete hypocrite. Friars were supposed to take oaths of poverty and chastity to better replicate the life of Christ; however, the Friar in Chaucer's text loves food, cons people out of money with sweet talk, and regularly seduces women (obliging him to marry them off and provide their dowries to hide his deeds). Chaucer could have easily torn into the Friar and decried him for being a fraud in his chosen vocation with choice nouns and a moralistic tone. Instead, he presents the Friar's personality and deeds in a rather matter of fact manner:
A Frere ther was, a wantowne and a merye,
A lymytour, a ful solémpne man.
In alle the ordres foure is noon that kan
So muchel of daliaunce and fair langage.
He hadde maad ful many a mariage
Of yonge wommen at his owene cost.
Unto his ordre he was a noble post.
Ful wel biloved and famulier was he
With frankeleyns over al in his contree,
And eek with worthy wommen of the toun;
For he hadde power of confessioun,
As seyde hym-self, moore than a curát,
For of his ordre he was licenciat.
Ful swetely herde he confessioun,
And plesaunt was his absolucioun.
Chaucer also balances out the Friar's many sins with how jolly he comes across to other people, claiming people like to have him hear their confession since his absolutions are "pleasant." The audience might recoil at the Friar's hypocrisy, but Chaucer makes clear why someone would want to be in the Friar's company. He might be a rogue, but he is a charismatic one all the same.