There are a wide variety in the world we live in. There are people who are born with sexual organs of both male and female, (in days gone by they where sometimes all surgically changed to females in infancy) There are people who carry both male and female chromosomes, (XXY) who appear to be male externally, usually have “micropenis” or very small penis and testicles when they become adults, they also have fits of rage and a tendancy to psychosis.
As Catholics we have to remember two very important things. Each of them has a soul. Each of them needs to be treated with dignity because they have an immortal soul and part of that dignity is in following the teachings of the Church on moral issues. If someone has a predominatly male physical sexual charictaristics at birth, we treat them as a male, the same for one who is predominatly female. If someone “changes” Sex later (someone born with no ambiguity of sexual charictaristics) we still treat them with dignity, but we would not be helping them by ignoring the moral teachings of the Church, and allowing them to marry someone of the same sex. (Remember a doctor can fill them with hormones and do surgery, but cannot change the DNA of the person)
The second important factor to remember is we live in a world that is not the ideal world planned by God. We live in a world where original and actual sin has caused sickness and death. Where evil presents itself as good, and immorality as morality. Love of God bids us to be an example of charity and Love to our neighbors, but does not command that we call evil, good. If we do not show the joy that comes from living a life in harmony with God, those who follow an immoral path will have no reason to investigate living a life in harmony with God’s will.