This article contains fan theories about Dr. Arden being the Boston Strangler. It is separate to avoid contaminating the main page with spoilers and speculation. It is subjective.
Dr. Arden is the Boston Strangler
In an interview with EW Ryan Murphy hints that Dr. Arden's true identity is revealed in those photos in his bedroom (which depict barely dressed women bound and bruised).
The first season of AHS embellished on the unsolved murder of the Black Dahlia. Perhaps this was the establishment of a tradition.
Albert DeSalvo confessed to the sexual molestation and murder of thirteen women in Boston, Massachusetts, between 1962 and 1964, that had been attributed to whom the media had dubbed The Boston Strangler. However, he was never charged (for those crimes anyway) as their was no linking evidence and discrepancies in the murder methods. This provides the writers with a wonderful opportunity to play loose with history.
Arden appears to be right-handed. It is "common knowledge" that the Boston Strangler is a leftie.
The writers have already begun to elaborate on the history of Anne Frank. It might be overkill to have two forays into speculative fiction.