I, for one, welcome the inescapable conclusions derived from bureaucratically-compelled inquests into inherently humorous and light-hearted happenings.
The last article I read was an American high school football coach using the word Nazi as a play call against a school that's 90% Jewish and the players using antisemitic slurs throughout the game.
That deserves an investigation and firing, this kind of Tom Foolery requires an eye roll and a change of call sign, if that.
It's my understanding that pilots don't get to choose their callsigns. Instead, it's their teammates who choose them, which is why they are often jokes at the expense of the pilot. E.g. the callsign of Ewan McGregor's brother was OB-2.
I saw a headline regarding this the other day, it called it something like "offensive call sign" and I immediately thought it would be something deeply awful and probably racist. Imagine my relief when I read on and learned it was instead something stupid and sophomoric.
The pilot deserves no more than a talking too for making a silly joke.