Worse than a murder
Talmud in Arakhin 15a states that “one who utters malicious speech with his mouth is a more severe sinner than one who acts.” As we already know, the punishment for malicious speech is a variety of skin diseases, usually translated as “leprosy.”
The connection between the “hidden sin” of the malicious speech and the visibility of the skin afflictions is clear. Sinning “in private” is still sinning. The later exposure of the sinner to the community and the lengthy and costly purification ensures that the others will think twice before spreading the evil slander.
However, there is a modern angle to the commandments, prohibiting the malicious slander. Torah concentrates on gossip about private people, but evil and deceitful propaganda directed against another country is no less slanderous. It inevitably leads to murder and destruction, as we see in the ongoing war against Ukraine perpetrated by Russia.
Every propaganda lie is the cause of countless death and immeasurable suffering, as has been stated in Talmud.