Many Knights lived by a code. Certain rules they did not break. It is these Knights that were remembered and reveared. While others of the title were lawless, they strove to be lawfull and meet the lawless on any battlefield.
Here is the oath from the Kingdom Of Heaven. Wether historically correct or not. It does give an insight on those rightious Knights:
Be without fear in the face of your enemies.
Be brave and upright that God may love thee.
Speak the truth always, even if it leads to your death.
Safeguard the helpless and do no wrong.
That is your oath.
"It is not what goes into your body that defiles you; you are defiled by what comes from your heart."-Jesus Christ, Mark 7:15