Used to have a lingering dread of seeing a certain ex boss at professional events, but so far so good after 7 years.
Yet somehow he cropped up, as someone I met at an event a couple months back reached out after seeing my Linkedin, saying "LWZ, did u work w ABC when u were at XYZ ?"... I just decided to engage on how this person knew my ex boss and to talk about the ex company itself
Feeling angry and emotional is perfectly fine IMHO, we are human afterall. Just remember that our career and life are not worth ruining over such idiots.