The reason why nature 'invokes random genetic changes and promotes diversity' is exactly that - random, it's because of chance.
Any argument in opposition to 'fixing' Transsexual-ism based around natural selection is a bit bizarre, given that transsexuals require an awful lot of artificial, unnatural changes in order to pass on their genetics, if it is even possible for them to do so. Natural selection either condemns these people to live in a body they don't feel is the correct gender, presumably for a life of unhappiness, and allows them to pass on their genes, or causes them to be an evolutionary dead end if they switch genders.
I refuse to accept that humanity, or genius, would die out if transsexuals no longer existed, it's called the slippery slope fallacy for a reason.