The Worst Blemish:

The Chida zt'l (Sefer Pnei Dovid) writes: "I heard that motzi shem rah causes a blemish to the bris halashon (the covenant of the tongue). And when a person blemishes the bris halashon, he certainly also blemishes the bris hama'or (a Kabbalistic term used to refer to the covenant between Hashem and the Jewish people)." The Sefas Emes zy"a (Parshas Metzorah 5650) writes: "It appears to me that blemishing the bris halashon is even worse than blemishing the bris hama'or.” He brings proof to this from a metzorah (who contracted tzoraas as a result of forbidden speech), who must be sent out of all three camps.