Those who lash out and behave in ways you would term “rude” are hurting inside.  Does this excuse their behavior?  Not at all, but this awareness helps you to not return their behavior in kind, but to be kind instead.  Such kindness may just jar them enough to feel what it is they feel they are missing.  Rudeness is an easy reaction.  Kindness becomes the norm when you set that intention, no matter how challenging.