For this type of thing I try to 're-frame' it in my mind as a lesson learnt, and that also (despite everything I'd hope in the world) there are some crappy people out there and I feel kinda sorry for them.

Turn your anger into sympathy for him, imagine what type of person he is and the daily life interactions he has had and will have with people that make him act this way.

Don't let his life actions affect your life anymore, remove the power he has over you.

(I feel I got a bit hand wavey there, sorry, but I find it really does help me, at least).