As I understand it, to "bingo" someone means to harass him/her about his/her decision to be childfree, typically using arguments that the childfree person has heard about a million times before. Someone (not someone on this forum, I think) made a funny "breeder bingo" card listing some of the phrases that come up again and again--for example, "it's different when it's your own," "don't you want to give your parents grandchildren," "you were a child once," and "who will take care of you when you're old." You can see an example of it here:
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