Once I figure out who's shitty (especially after delayed processing days, weeks or months later) I just stop positive engagement with them. They never have to know what I figured out. Leaves room for other to fill the void and life is better.

If I really don't like them I tell them exactly why. I've got sputtering responses that fill me with warmth years later each time I remember or tell the story to someone I care about.

People are not often bluntly confronted on their own shitty behaviour and there is a power over them when they know your know.