Final answer:
Harry Hay left the Communist Party for multiple reasons, such as his disagreement with the party's politics, the CP's suspicion that he was an FBI informer, and his desire to protect the party from anti-gay attacks. Furthermore, his expulsion from the CP was also influenced by his public identification as a homosexual.
Step-by-step explanation:
According to the authors Michael Brace and Leslie Feinberg, Harry Hay left the Communist Party (CP) because he no longer believed in its politics. However, the CP feared that Hay was an FBI informer, so they expelled him. Another reason given by Hay himself is that he asked the CP to expel him in order to protect the party from anti-gay attacks. Lastly, the CP kicked out Hay after he gained notoriety as a homosexual.
Learn more about Reasons for Harry Hay's exit from the Communist Party