I think you're mistaking the purpose of the 1st amendment. Racist comments are protected speech in that the United States Government cannot arrest/imprison/etc. you for that kind of speech.

Freedom of speech does not mean freedom of repercussions for your speech. New York is an at-will state, meaning there is no legal problem with this email. There is no protection for people getting fired for hate speech, just like there is no legal protection for people boycotting or refusing to work for companies that they disagree with.