Maybe not the smartest thing to be singing at that moment, but does it deserve this much attention?
Can understand how people not familiar with military think pilots should act professional all the time but that is just not realistically achievable.
Specially if you understand a pilot that has seen much instant death create some form of psychological shield against the horror side of it all.
Once they're back in normal life, when there is no need for the shield, to life without it, now there is the trouble.
I don't hear or read anything about this in these stories, all the focus is on how a pilot could do something fun while preforming his job (war).
This opinion stands clear from what war is and is used for, i am looking at why a (human) pilot would do something like this.