A vulgar or malicious person can only utter rude or offensive remarks; one cannot expect pleasant words from such a person.
他总是喜欢说些挖苦人的话，真是狗嘴里吐不出象牙。
He always enjoys making sarcastic remarks; truly, a dog's mouth won't spit out ivory.
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A vulgar or malicious person can only utter rude or offensive remarks; one cannot expect pleasant words from such a person.