Sometimes understanding why someone hurts others helps you to just sit in understanding rather than hurt. It gives you a space in which to make a more informed and intentional choice about how you want to react. It gives you a chance to decide whether or not you will fare well being around this person or people like them. You may even find that being around them might be good for their welfare. So, if you are so inclined and if you can handle it give it a try.
This space I speak of is not an element of time but rather a suspension from reactions, judgments, and self-talk that pops up whether or not it is wanted when people do or say mean or hurtful things. It takes practice and sometimes the response to these people is so automatic, it is in your head and most likely out of your mouth before you can open the space of suspension. In the end each person must decide for him or herself when or if enough is enough and to decide whether or not you want this person in your life. If you do it for the right reasons and not out of anger or hurt I think it will be better for you. I have no scientific proof of that. Take a leap of faith. I promise it won’t hurt.