You sound like a kind and sensitive person who doesn't like to hurt people. Sometimes we say things without thinking. When I do that, I can hurt others too. I think you were under time pressure (needing to leave for your appointment) and the teacher startled you with that comment and you reacted. You didn't mean to hurt anyone but it happened. I agree with healingme4me that the teacher could have brought up the topic in a different way and also privately.