If someone is behaving with you in a way you think they should not, what you should NOT do is return them with greater disrespect.
What goes around comes around.
So be kind and bless those who harm you, because before them you are being kind to yourself.
What about the other person’s misdeed? Just remember that we are here to take care of our own karmas only, not anyone else’s. There is a perfect balancing system that acts to take care of everyone’s karmas.
Look within, and without shall be taken care of.