Condoning sin, participating in sin, and failing to correct are all sins in themselves.
From the Catechism:
1868 Sin is a personal act. Moreover, we have a responsibility for the sins committed by others when we cooperate in them:
- by participating directly and voluntarily in them;
- by ordering, advising, praising, or approving them;
- by not disclosing or not hindering them when we have an obligation to do so;
- by protecting evil-doers.
1869 Thus sin makes men accomplices of one another and causes concupiscence, violence, and injustice to reign among them. Sins give rise to social situations and institutions that are contrary to the divine goodness. “Structures of sin” are the expression and effect of personal sins. They lead their victims to do evil in their turn. In an analogous sense, they constitute a “social sin.”
2284 Scandal is an attitude or behavior which leads another to do evil. the person who gives scandal becomes his neighbor’s tempter. He damages virtue and integrity; he may even draw his brother into spiritual death. Scandal is a grave offense if by deed or omission another is deliberately led into a grave offense.
2285 Scandal takes on a particular gravity by reason of the authority of those who cause it or the weakness of those who are scandalized.
Jesus had this to say, Mt 18:6-7:
“Whoever causes one of these little ones* who believe in me to sin, it would be better for him to have a great millstone hung around his neck and to be drowned in the depths of the sea. Woe to the world because of things that cause sin! Such things must come, but woe to the one through whom they come!"