Learn English – A word/phrase for someone who is very sensitive to slights/injustices committed against him

I am trying to think of a word, or if necessary a phrase, to describe someone who is extremely sensitive to minor injustices committed against him. Think of a person who will challenge anybody to a duel who treats him unfairly, even if the offense is slight.

The word proud comes to mind, but it has other connotations and doesn't capture the sensitivity I am trying to express.

I am not looking for synonyms for sensitive, like thin-skinned, etc. I am not talking about someone who can't handle a joke or the rough and tumble of normal conversation. I'm talking about someone who will never take an injustice lying down, even if it's so minor most people would say "let it go".