What's a word for a blamer who blames others for their own guilt?

Solution 1:

Projection might be what you are referring to.

From https://en.wikipedia.org/wiki/Psychological_projection:

Psychological projection is a theory in psychology in which humans defend themselves against unpleasant impulses by denying their existence in themselves, while attributing them to others. For example, a person who is rude may constantly accuse other people of being rude.

According to some research, the projection of one's negative qualities onto others is a common process in everyday life.

In short, the person would be said to be projecting.