If we accept that the murderous arsonist’s letter, of February 22, 1915, was written by Freud, the obvious question is whether other similarly murderous letters, in the published collection of their exchange, even though ascribed to Ferenczi, were authored by Freud.
Thus, In the letter of October 27, 1914, written four months earlier - yet another murderous confession - allegedly Ferenczi wrote: on account of a slight injury to my homosexual complexes, I would like to perpetrate mass murder (arson). (1)
Considering Freud’s homosexual complexes, and his predilection for murders and fires, this sounds more like Freud than Ferenczi.
And it was Freud, not Ferenczi – who suffered a slight – in Freudian newspeak a bad – injury to his homosexual complexes when he lost his beloved Teutonic crown prince, Jung, only a year earlier, in 1913.
Further, the letter's author disclosed that he had already committed criminal acts.
This confession is, he wrote, an admission … that I …  have these [murderous] desires even now and also allow them to be actualized once or twice a year. (1)

Addicted to his penis

Freud’s legendary masturbation followed him throughout his life, he even included it in his theorising. He also mentioned it in his letters to his boyfriend, Fliess, on 22 December 1897
As he informed him, masturbation is the one major habit, 'the primary addiction', and it is only as a substitute …  other addictions - to alcohol, morphine, tobacco, and the like come into existence. The role played by this addiction in hysteria is enormous; and it is perhaps … my major, still outstanding obstacle. (2)
Thus, Freud’s incessant masturbation resulted, not only in his lifelong addiction to tobacco, and cocaine but also in his hysteria - not necessarily in this order - and it was his masturbation that was the major …  obstacle to him becoming “normal”. (It never happened.)

Scarred for life by the primal scene

Moreover, it was Freud who, in his partly fictional story of Wolfman (1918), coined the term primal scene denoting witnessing one’s parents having sex. Already, 21 years later, in the letter to Fliess, on May 2, 1897, Freud mentioned this notion. (3)
And, in the Interpretation of Dreams, Freud described having witnessed the primal scene, and his reaction to it in the form of calls of nature. (4)
As he revealed, Freud was severely reprimanded by his father for his actions.

Freud fulfilled perfectly the three conditions that point to him as the author. of the letter of October 27, 1914, who has the murderous need for setting fires:
1. the compulsion to masturbate  - Freud's main addiction
2. the primal scene - seeing his parents engage in intercourse
3. urination - relieving himself at the sight of the primal scene.

A petroleur 

As it is obvious, Freud didn’t keep his penchant for arson secret, at least from his boyfriends. Already aged 12, Freud displayed this kind of incendiary aggression. Hence, in the letter of August 15, 1877, to his boyfriend at the time, Eduard Silberstein, he announced: I have not enough hate to express my feelings ... In times like these one is tempted to turn into a petroleur [a fire-bomber]. (7)
Whether the young Freud turned words into action, then and there, is unknown but not impossible.

Without a doubt, Freud was a murderous character, employing, among others, arson as a means of destruction of property and human life.
If you want to kill lots of people in one go, burning the house, they live in, in the middle of the night, is a splendid idea. Actually, from an arsonist's point of view, burning a theatre with hundreds of people is an even better idea. Bud did he?