We react as if the person intentionally snubbed us.
Contrast that with what the scriptures teach us. In today's first reading St. Peter challenges the people, and therefore us,
as he who called you is holy, be holy yourselves in every aspect of your conduct
But when they are not holy, notice how he describes it
do not act in compliance with the desires of your former ignorance (1 Pt 1:14)
Like Jesus on the cross St. Peter attributes the behavior not to malicious intent, but ignorance.
Is it possible for a person to act with a truly malicious intent? Certainly. But should that be our instantaneous presumption? No! If we are Christians we start with the presumption of ignorance. It is actually a double ignorance, their acting in ignorance and our ignorance of what is in another person's heart.
Does it change the person's behavior? No, but it changes our response. We no longer react with that flash of anger, that can turn into a lasting grudge against someone.
If we can train ourselves, and it does take practice, to presume ignorance until we have proof of something else, then we can be more peaceful in our own hearts. It is not our natural response, but with God's grace and lots of practice, it can become a habit.