air (one's) dirty laundry in public
To discuss very private, personal matters, especially that which may be embarrassing, in public or with other people. It always makes me uncomfortable when John starts going into all his personal problems whenever our friends get together. I just wish he wouldn't air his dirty laundry in public like that. People have an unnatural fixation on the personal lives of celebrities, but I don't see why they should be expected to air their dirty laundry in public.