That's rationalization.
The legitimate, moral purpose of drugs, devices and surgery is to restore, repair, or strengthen normal physiological function: the natural design. In other words, ethical medical practice is to cure diseases, heal wounds and injuries, strengthen failing organs and systems, taking the healthy normal design as the pattern and goal.
Some people are so alienated from their natural bodies that they seek to fundamentally alter or impair them. There are weird body dysphorias where people with healthy eyes want to have them removed, people with healthy limbs want to be amputated, people with a male physiology want to be castrated and treated with hormones to achieve a pseud-female body-form, etc.
I think you would agree that it would be unethical for a doctor to castrate or maim a person with the non-therapeutic removal of a healthy eye, a healthy leg, a healthy penis and testicles. This is because the ethical purpose of the medical arts is to work FOR, not AGAINST, the purposes for which that organ was created.
All this does not necessarily apply to veterinary medicine, because animals can be re-engineered on many levels to suit human purposes. Animals can be bred, can be hybridized, can be sterilized, can be induced to develop in ways that they would not develop in the wild. But none of this applies to humans, because we, unlike animals, were not made as objects for the use of another species, but rather, we are persons made in the image and likeness of God.
That recognition of the imago Dei is the basis or morally good health care for humans.
This is why directly intended contraception and sterilization are quite different from the ethical practice of medicine. Here the intent is to partially or totally, temporarily or permanently, deprive a person of natural bodily integrity and function.
Interestingly, the whole homosexual/tranny ideology is based on the same premises as the contraceptive ideology:
Those who accept these deviations --- contraception, homosexuality, transsexualism --- have this in common: they reject the God-given design of sexuality; they reject the idea that the sexuality God gave us is sacred; they assert an autonomous right to deconstruct natural sex and gender.
And they impose the re-definition of words so that fully functioning heterosexual sex is redefined as oppression; fertility is redefined as a glitch, not a feature; pregnancy is dealt with as an illness (remember when Clinton's Surgeon-General, Joycelyn Elders, called pregnancy "America's most serious sexually-transmitted disease"?) and the chemical/surgical shutdown of female physiological function is redefined as "women's health."
It's all around us, metmom: the rejection of natural sex, complete n every detail, as if it were God's worst mistake. May God have mercy on us all.