The Catholic Catechism is very clear on the sin of Calumny.
I will put this hear for all to read.
2477 Respect for the reputation of persons forbids every attitude and word likely to cause them unjust injury. He becomes guilty:
– of rash judgment who, even tacitly, assumes as true, without sufficient foundation, the moral fault of a neighbor;
– of detraction who, without objectively valid reason, discloses another’s faults and failings to persons who did not know them;
– of calumny who, by remarks contrary to the truth, harms the reputation of others and gives occasion for false judgments concerning them.
God is good.
JMJ, Pray for us.