Someone near to me (not giving out too personal details here to not offend her) has BPD. (Borderline Personality Disorder). Very often people with this particular illness will try to project their own feelings onto others. For example, when they are unhappy or feeling bad about themselves they (attempt, and very often succeed from what I can see) attempt to project and create these feelings in others around them.
When this person was having an affair she continuously “projected” unfaithfulness on her husband (at the time)—accusing him of unfaithfulness and hyper-criticizing his normal interactions with others as being sexual or disloyal, etc. The kicker is, of course, that she was the unfaithful one having multiple partners…but she made him feel constantly as if it was he who was unfaithful and not trusthworthy.
The quotation “The lady doth protest too much, methinks.” from Shakespeare’s Hamlet has come to mean that one can “insist so passionately about something not being true that people suspect the opposite of what one is saying.”...I think that neatly summarizes a lot of the sort of projection I’ve seen in the past. So, question the accusations you’re hearing projected onto others when they seem especially vehement..