Not due to the song, exactly. I wanted to use a song title that I liked and that sounded good for a username.
But, I chose BohemianRhapsody because of the following definitions:
Bohemian- a socially unconventional person.
Rhapsody- an effusively enthusiastic or ecstatic expression of feeling.
I took that second one as also something cathartic.
So therefore, a Bohemian Rhapsody would be a socially unconventional and very enthusiastic expression of feeling.
I was about to make an account on "Sociopath Community" so I thought such a name would be subtle, ironic, and amusing. I also thought a Bohemian Rhapsody sounded a lot like how my personal streams of consciousness (some of which I would come to post on SC) end up being.
And thus, I selected that name.