In other words, it is nature that made the fundamental mistake--not the individual in question...
Not quite. AFAIK, no leftists have come out in favor of transracialism. That’s mostly conservatives having fun.
IOW, sex (pardon me, gender), which is imprinted in the DNA of every cell, is mutable and someone’s “identification” must never be disputed.
Race, which they claim (or did until recently) is a social construct that doesn’t really exist, is immutable and a person’s self-identification is irrelevant.
Sexual orientation is also, according to them, inborn and immutable. Attempts to help someone change it are hate crimes and must be prohibited by law.
When medical technology becomes advanced enough, they would be perfect donors for brain transplants, into brain damaged patients of the opposite sex.
Of course they'd still be crazy.