A few points:
- I would rather have the penis I was born with, which would now include not a 'small ribbon' but an area of skin with the approximate surface area of an index card
- There are far less invasive treatments for penile cancer than the removal of the entire penis
But... becoming a girl because you have cancer and lose your penis? Are you for real? It's funny you mention that though, because there's a notable case where circumcision itself did destroy the penis of an infant, and in attempt to fix things they performed gender reassignment surgery (though doomed sexually for life), put the kid on hormones and raised him as a girl. Problem was, he never identified as a girl, and some decades after learning the truth about what happened to him, killed himself.
But yep, the science behind the procedure is bulletproof. Except when it isn't.
And to your assertion of cognitive dissonance, I have not experienced this. To the contrary I have found that people will go to any length to convince themselves that they have not been harmed when it's very obvious they have.