Still actively despise my ex... after 6 years

I know this is abnormal and I probably need some therapy.

I broke up with an ex 6 years ago, for a lot of reasons. He was aware of why I left him but to save face to his friends and family he concocted the story that I cheated and then he caught me in the act and kicked me out. For the following year, all his friends (it was a small town) harassed me, both in person and on Facebook. I was stalked, and humiliated and ended up moving to a different state.

I still come across his Facebook profile and it fills me with rage. Even more so, because his family encouraged it all, and even took part in some of the evil things that were done to me, but they play the uppity community leaders in the town where my parents still live.

It’s been 6 years. I’ve married, had a child, moved to 3 different states, finished college, bought a home... and yet I still can’t get over the absolute hatred I feel for someone I broke up with when I was 20. How do I get past this?