Ibn Ezra translates yecheratz l’shono as bark or bite, which gives point to the following story.
Jews were often scared of dogs, especially in Eastern Europe, where the pogroms involved setting ferocious dogs loose on the Jews.
It is said that someone came to his rabbi and said, “Rabbi, I am frightened of dogs!”
The rabbi replied, “Don’t worry; the Torah says that no dog will attack one of the Children of Israel!”
“That’s all very well, rabbi,” said the man, “But how do I know the dogs understand Hebrew?”
Fair enough. The sages had a poor opinion of dogs, however, long before the pogroms and the Cossacks. Even in ancient days the dogs would prowl in search of food and would often bark or howl all night.
The sages said, “Anyone who indulges in evil talk (lashon ha’ra) deserves to be thrown to the dogs”. The connection with dogs is probably that evil talk uses (or rather, misuses) the tongue, and the verse about dogs also mentions the tongue.
The dangers of evil talk are constantly emphasised in Judaism, and many of the Yom Kippur confessions have to do with sins committed with the tongue.
Warning that malice and gossip would be severely punished is the message of the rabbinic interpretation that the leper, the m’tzora, is suffering because he was motzi ra, “the utterer of evil”.
In the case of our verse, the sages were quite literally telling people that because of evil talk they would go to the dogs.
It’s not entirely fair to the dogs to be demonised in this way, especially since Biblical and rabbinic literature are well aware of dogs as loyal friends, but preachers often cannot avoid the temptation of bringing folk prejudices into their homilies.