I am so angry. Libra's mouth is poisonous. I'm just talking to him. He always belittles me, but I still can't find a way to talk back.

Your quarrel has nothing to do with the constellation. Whether he is a Libra or a Pisces, he likes to belittle you, which shows that his character is like this. He likes to belittle and attack others with vicious language. It's normal to get angry because you can't find a way to talk back. I think it is possible that he has been belittling you because you are very good friends. He dares to belittle you so much that he thinks you don't mind. But in fact, if you mind, or like you, you will be teased. After all, that boy won't always belittle a person unless he eats too much and has nothing to do.