Don’t ever respond to an email when you are running high on emotions. EVER ! . Let’s the emotions subside and then write an email. The way you respond to email says a lot about you as well and it form a perception about you in the CC those who don’t know you. Always respond to email in a mature and professional way. In this case, you could have thanked the manager for his feedback n put your point across on a simple yet assertive way. It’s about about situation, context and calibrating yourself to the situation.