Sure there is:
https://www.youtube.com/watch?v=crIlBVCSPjg
And it would seem you agree then that wanting to cut off your penis is basically the same thing as cutting off your leg.
No. I wrote that wanting to cut off one's penis can be rational. And wanting to cut off one's legs can also be rational. That doesn't mean that anyone who wants to cut off their penis also wants to cut of their legs.
But do try to keep up. And thanks for your intellectually dishonest attempt at oversimplification.
The only rational reason to want to cut of a body part is an ailment. That seems pretty simple.
OK. Then if the "ailment" is that the existence or lack of a penis is causing a person great suffering, and a mental health practitioner with extensive training in this area evaluates the mental state of the person and determines that the person's suffering is caused by a rational and unalterable perception that the person is of a different gender than their physical body, you agree that wanting to add or remove the penis is completely sane. Because as you've stated, an "ailment" is justification for removing (or adding) a body part.
So the only thing that determines mental illness is "happiness"?
No. You've conveniently removed the word "rational."
Again, thanks for the intellectual dishonesty.
So if a person is "happy" hearing voices in their head then they aren't mentally ill?
If a person hearing voices in their head is diagnosed with schizophrenia, then they're mentally ill. But if a thorough diagnosis determines that the voices in their head are caused by an implanted radio receiver, then they're not mentally ill.
The problem you're having is a lack in imagination. You're unable to imagine that there are many, many possible causes for a person's thoughts and beliefs. You're unable to understand that your inability to imagine a rational and compelling reason that a completely sane person might want to remove their penis (or other body part) doesn't mean that everyone with that desire is mentally ill. In your universe, there are only a few possible explanations for human behavior, so you label people "A" or "B" simply because you aren't smart enough to understand that "C," "D," and "E" also exist.
To put this another way, you're guilty of circular reasoning. You're assuming that anyone who wants to add or removed a sexual body part MUST be mentally ill. Yet pretty much all of the major mental health bodies now recognize that being a transgender person is not a mental illness. But of course you know better.