You misinterpret people's actions as characteristics, or attributes of their character. People tend to say the reason a person does something is because of a character attribute of that person. A fundamental attribute is a characteristic describing who a person is at their core.

Most of the time, you and I are not acting out of our fundamental attributes. When we do or do not do something it is actually because of the circumstances that we are in. The error is actually that we are applying a fundamental attribute to describe the action of a person instead of allowing for the circumstances in which a person acted or didn't act to describe their behavior.

We need to ask these three value seeking questions.

What do I already know about the person outside of the context of this one incident?

Is there something that could possibly be causing them to act the way they are acting?

Is this behavior part of a long standing pattern, a new forming pattern, or is it an anomaly?

You really are responding to the dynamic world around us. You are not the sum of your actions. Because we are not applying our actions to describe our fundamental attributes, we should not do that to our neighbors.