I consider the weapon "Kwan Dao" the weapon of virtue becuase of how it was represented and made famouse by Gen. Kwan Yu. Gen. Kwan Yu was known for his martial virture, he was a very righteous person, loyal and would not hesitate to take up the cuase of the oppressed.
Aside from his strong moral character he was also a very skilled martial fighter and a good general. He showed unmeasurable bravery, courage, virtue and loyalty to his emperor and the people that he defended and served.
He was well respected by his enemies that when he was captured they try to convinve him to switch side but Gen. Kwan Yu refuses to betray his emperor, his people and his country he was executed with honor, given a heroes death he died as a true respected warrior.
Gen. Kwan Yu exploites soon become legendary, after his death people started venerating him and soon he became a WARRIOR SAINT OF MARTIAL VIRTUE.