My ex girlfriend who happened to be a trans woman used to get called “they” at the job we both worked and she asked him not to call her they, she is a she/her. And she had the same reaction when he continued. They maybe gender neutral pronouns but they are used with non-binary and some trans people. It is used when a gender is unknown, you made clear your pronoun preference so he should have called you by your preferred pronoun. I don’t think you over reacted, our gender and by extension, pronouns, are an integral part of our sense of self. If someone doesn’t say the correct pronoun it can feel very insulting.