A fundamental problem with the diagnostic labeling of psychologically disordered behaviors is that the labels often

The problem is the label often bias our perception of the labelled person.

Explanation:

It is normal to have a certain perception we impose onto people which makes it easier for us to go through this world. However, people tend to accept labels we impose onto them and behave in the certain way which is in accordance with the label. Naturally, they may behave in other ways. Nevertheless, our perception of the behaviour may not be the correct one. Labeling theory is associated with the concepts of stereotypes or self-fulfilling prophecies.