What does your gut tell you to do? You cant listen to your heart, it will screw you over more often than not if its answers you seek where the other party sucks. with someone u love like or want that's blown it with trust or warmth. If your like me you probably choose not to and really should listen to your brain, its telling you to be equally un adult and harsh back. So trust your gut. Sense its in the middle, your evaluates both sides and will no best. THATS my advice but here is my opinion--
History repeats its self. He may never do or say unnecessary cold mean things again but those chances are slim. I don't know how mature he is but that is not ok to say to anyone little on your girlfriend. If you let him get the idea that your ok with verbal abuse he will continue to do it and maybe more. Be careful good luck and trust your gut before anything else.