As I get older I still identify as a young person. I still feel vital and I'm always surprised when I look in the mirror and see what time has made of me. I am also increasingly uncomfortable in and with my body often wishing to "turn back the clock"
In fact
Many people resort to surgery or other cosmetic measures in an attempt to "pass" as younger people.
Is it wrong to want to be younger and to want others to think we are younger?
If it isn't wrong then what is wrong with wanting others to view you as a different gender than you were assigned at birth? Even if it were not true. Even if nothing you do can ever make you a different gender than the one written on your birth certificate?
Now consider for a moment the possibility that the gender on your birth certificate is not like your age and may not actually accurate. That it may in fact be incorrect for a number of physical and psychological reasons.
Let's say we disallow all cosmetic surgeries, both those meant to help one "pass" for younger and those that allow one to "pass" as a specific gender identity. Are you still opposed to the idea of a person in this position dressing, acting and asking to be addressed as that gender (whatever that means to you or them)? If so may I suggest that it isn't the surgery that offends you so much as the very idea that someone would have the audacity to challenge your views on gender roles.
This isn't meant as a strawman. I'm sure not everyone who opposes cosmetic surgery feels this way but it is worth asking yourself if this does in fact apply to you and if you are ok with that.