Those people have a vested interest in seeing things their own way. To accept your version of events probably means having to accept responsibility that they don't want to accept. They're going to have their own way of seeing things that makes it possible for them to live with it.
I think that a related issue can be a deep-level fear of confronting the perpetrator(s). Perpetrators can be people who use power over others in a pretty dangerous way, and I think that peoples' monkey brains can tell them to defer to that person, take that person's "side", etc. without "conscious" awareness, whatever that is... (It's safer to be a "friend" of the big strong monkey! The abused person often has much less power.) I think that supporting unjustly used power semi-consciously causes huge problems in our society in many ways.
We also may all be influenced by this dynamic in more innocuous ways. I've never seen research on this though; the people setting research agendas tend to have power...