I think the reaction of being offended itself is a pretty strong , even dominant reaction that in a less civilized setting would prompt an individual to fight and establish their standing and respect from others. If you look at any group where hyerarchy matters, like mafia, gang or a tribe, disrespect is taken very seriously and has to be dealt with. If people in that environment just took it, they would lose respect. The anger it provokes in them pushes them to act on such status thereatening provocations.

Now however we are in a civilized society and cant beat someone up or kill them/have them killed because we are offended. We need to be reasonable, non violent. But offense still triggers emotions, except we can only react impotently by complaints and verbal outrage, which shows weakness. Now a civilized, reasonable, "strong" human simply doesnt get offended but resolves conflict rationally and calmly, trying to compromise, reason with, or ignore the offender (which is actually a weak response.)

We are just adapted for the environment we no longer live in and some deal with it harder than the others.