Why is chopping vegetables with your left hand ridiculed?

Maybe you misunderstood. I think people who are used to their left hands are special. As for what you said about being laughed at by others, maybe you misunderstood. There are many kinds of smiles. I guess the people who laugh at you are not laughing at your imaginary meaning, but that you are different from others. It's just a reaction in your heart. This is no joke. In fact, after reading your question, I am also laughing at your wonder. Why do those people laugh at you? This is a curious psychology.