Is it okay for your best friend to kiss your most recent ex boyfriend?

Long story short -> my best friend introduced me to this guy, months and months later we dated, he turned out to be a dou.che, he hit me, etc. we broke up, my bestfriend and him are still friends, and she told me they were hanging out today and they kissed... is this okay? i have no feelings for him at all but I'm still quite mad..