We should not...no... we cannot go into this world where so many people are hurting and refuse to be kind. Being kind to others is just another way of showing we care. It is not something that can be faked, you can try to "fake" it, and even get away with it for a while, but eventually you will just go back to your old way. Did you know true or authentic love (kindness) puts others needs before their own? This type of kindness has to flow from a real and true relationship with Jesus. You know and realize that Jesus loved us when we were undeserving...yet he loved us anyway. When we follow the example He gave us, we can't go wrong.
But what if they have been mean to you...shouldn't you be mean to them? I think you know the answer to that...but do you practice it? Be kind to them...as my mom use to say..."Kill them with Kindness". They won't know what hit them. I personally enjoy being kind to people, it so much better than the alternative.
If you begin to find yourself not living out love in your life...reevaluate where you are in your relationship with God and start practicing kindness to everyone (even your family)...Love is Kind.