I'm left handed.
I remembered once when I was in Mina in one of the Tashriq days. It was during the evening after we finished the stoning for that day. So, I met this Saudi kid. We started to talk and he listened to me because me and my dad were the only Malaysians in the camp. So, he asked me about the country, about his English, about the Qur'an. We talked merrily. So, then he asked me to come to his camp for a while. I followed, seeing no harm in doing so. So, he asked me to give him my email. He said he wanted to contact with me and improve his English. So, he took out a paper and a pen. I held the pen and wrote down my email. He was surprised that I was using my left hand. He said, "What is this? Not good, not good!" And I was just silent there, I didn't want to start anything.
I have the same case as you do, although people don't treat me differently as much as they do to you. I do everything with my right hand, even eating. The only thing that I do with my left is write and all other educational-related things. I have friends in my class who are also left-handed.
These people who treat left-handed people are irrational. And worse, if that person is a Muslim, he is not acting as one. Allah S.W.T. has created me and made my left hand dominant. I cannot change that, so no one can and no one will. Muslims who object people using their left hands to write are not good Muslims. I know it is the Sunnah to use your right hand in everything and that eating with your left hand is bad as the Shaytan eats with his left. But they must understand, Allah S.W.T created people with different abilities. It's not like I chose to use my left hand for writing. It just came.
Islam does not banish uniqueness. This is the thing that Muslims must understand. Being unique is not wrong in Islam.
May Allah S.W.T. guide us all.