This quote means it is not enough to know what is right; you have to do what is right.
Confucius was an early Chinese philosopher who postulated how to live a moral life.
Confucius stressed that all humans should strive to be jen, which generally means “humane.” Expressed by the character combining the meanings “man” and “two,” this concept called for people to be considerate and compassionate toward one another. (enotes)
This quote is indicating that people who know the right thing to do but are afraid to act on it are cowards. When a person knows what’s right, it is that person’s responsibility to act on it regardless of the risk. To not act rightly is less of a problem than knowing what is right and not doing it.
Let's say that a group of your friends decide to vandalize a house in your neighborhood. You do not think it is a good idea, but you do not want to go against your friends. You bow to peer pressure. This is cowardly, according to Confucius. You should not do what you do not feel is right.