The message at the heart of J. Edgar is to be true to yourself, or every part of your life will be based on a false foundation. The movie suggests that Hoover's inability to be honest about his own identity possibly contributed to an excess of zeal in criminal investigations of sometimes questionable legality.
A few scenes feature fist fights and shoot outs.
The undefined nature of Hoover's relationship with his assistant makes the question of sex, and sexual identity, an important part of the film. One scene involves a surveillance audiotape that seems to have recorded the sounds of people having sex.
Infrequent swearing; when the words "c--ksucker" and "f--king" are heard (in two scenes), they stand out since the rest of the film is so lacking in profanity. Also "for God's sake" as an exclamation.
Drinking, Drugs & Smoking
Some social drinking, though Hoover was a teetotaler and actively discouraged people from drinking, on and off the job. Some smoking (accurate for the time period).