JC,
Don't let that person push your buttons... you did a good job writing a very tactful email.
Some people may not agree with the idea of 'vengeance' (Jesus Christ didn't for one), but 'justice' is not the same word. Although people can interpret the word 'justice' in many ways.
If that person was reading more into the message about you, it sounds like they have some personal issues with you and are using the email for an excuse to lash out.
IMO you did a good job.
justice (jùs´tîs) noun
1. The quality of being just; fairness.
2. a. The principle of moral rightness; equity. b. Conformity to moral rightness in action or attitude; righteousness.
3. a. The upholding of what is just, especially fair treatment and due reward in accordance with honor, standards, or law. b. Law. The administration and procedure of law.
4. Conformity to truth, fact, or sound reason: The overcharged customer was angry, and with justice.
5. Abbr. J., j. Law. a. A judge. b. A justice of the peace.