In a conflict both parties are responsible for the interaction. It is almost never the case that only one party is entirely responsible. Blame is a way to try to place your own negativity onto the other person as well, so that they are responsible for your own failings too.
The way I think about it is the following: say a thief has a particular style, that he leaves messages on the walls of the houses he steals from: “XYZ was here” or something like that. Then, another thief, picking up on this, will use the same style to pin it on the first thief so that when the thief gets caught, he will be punished for the crimes of the second thief as well. In the same way, blame uses the other person’s negativity as an excuse to make them responsible for our own negativity too.
It is a very subtle exchange but very powerful and with many consequences. One of those consequences is that we feel victimized by the other and feel quite depended on them and afraid of them, because unconsciously we have made ourselves helpless in the face of their negativity. It is one side of the coin creating the other. The victim creating the persecutor. The moment we accept our own negativity, we take our power back and both roles dissolve.
“There are particular phases in human development where an entity finds it almost impossible to come out of his or her negative defense system, and of the conviction that this defense is necessary, unless one of those people with whom the person is entangled lets them off the hook by admitting his or her own negative intentionality, destructive attitude, dishonesty, and meanness. Just imagine how you would feel when someone close to you, who has given you pain by pointing out your real and your false guilts, but who has also confused you by the denial of his or her guilt, suddenly said to you: “I realize that I do not want to give you love. I want to demand from you and then blame you, accuse you, and punish you when you do not comply with my demands. But I do not allow you to feel hurt, because although I want to hurt you, I do not want to be made to feel guilty by your hurt.” Just imagine how this would set you free! How such an admission can suddenly clear up many confusions! It is not very likely that you would respond to this act of love by being self-righteous and acting the all-innocent one who has always known this and is now established as the innocent victim.
If you admit your similar unfair demands, your cowardice in giving your feelings, and your negative intentionality, it may indeed be hurtful for your pride, but truly for nothing else! The other who hears it has, in that moment, received a gift of love from you, even though you may still not want to love with your heart, with your feelings, with your inner being. But you have begun to love by being truthful.
By setting others free from the false guilt you have placed on them in order to conceal your own, you allow them to look at their own real guilt without self-devastation and without this painful inner struggle in which the mutual guilts and accusations are all confused. Release and clarification often lead to the solution of the deepest problems. It is as though the personality needed this “outer” grace, this helping hand. For the dishonest placing of guilt on others makes their true self-revelation almost impossible; it implies that if they admit guilt you are right in accusing them of being bad and of being the cause of your misery. This is how people are hooked together in denial, guilt-projection, either/or struggle, confusion, and negative interactions. Someone must begin to loosen the hook-up and disentangle the knots.”
– Eva Pierrakos, Pathwork Lecture #202: Psychic Interaction of Negativity