Why do they choose it?
Our Higher Minds' plan experiences down to a certain level of detail. In most cases, we would plan to be transsexual vs having it be something that went against our life's plan. Usually, these beings are some of the more advanced souls who have been through many lives on earth already and choose to take on more challenging lives for very quick soul growth and understanding of what others go through. The souls let go of a lot of personal karma perhaps picked up in other lives for being on the other side, judging transsexuals.
They also choose these lives to help the collective reduce their karma; by being of service to the collective and teaching them about judgment; learning about guilt and not taking things personally; being naive o darkness; deciding not to allow circumstances to affect your energy; and lastly, becoming empowered and teaching others how they can become empowered too.
In that process, they might decide to embrace their original sex or they might not. It doesn't matter because it is not a requirement for enlightenment. However, there are many (not all) cases where someone is confused about their sexuality because of abuses, changes in our hormones from our GMO food, and sexual perversion or focusing too much on sex.
There are also cases where a soul has advanced to higher realms and the more you advance the more androgynous one becomes. There are also cases where a soul chooses the experience of being a transsexual but with no other physical influences or challenges, they choose it just to have the experience.
How can we judge?
If there is no right or wrong and we are only experiencing different shades of gray or to put it another way, different levels and varieties of beliefs that we are separate from God when we are in fact not, then who are we to attack someone or even defend our own beliefs. When we understand or become enlightened enough that we know that in the eyes of God, who wants us to have these experiences in order to grow and know what love is, we are acting out our own truths. "Truths" in this case being varying levels of illusory separation from the ultimate truth that is God or love.
The experiences we have are only truths because they come from God's desire to know himself and in order to know himself, she creates the illusion that she has many parts that are separate. This happens so they can experience what God is like from the illusion of feeling separate. In the same way, in order to really know love, we must experience darkness. If we never experience the darkness then we never feel anything outside of love. To God, love would just be a state she has never felt because she has never known anything else.
what we resists persists
When we let go of resistance, defending, and judging we create this space. It allow those in lower vibration to heal their root chakras and their kundalini to rise and open other closed off chakras. In this way, we are creating a space for them to be compassionate but we shouldn't expect it. Nor should we force them to change because this would only create more force back at us since the universe acts as a mirror.
Transsexuals can also immerse themselves in their communities and show these people respect for their beliefs as long as they are not harming you physically. If you are a sensitive person then do more inner work to learn not to take things personally through understanding what the ego is and it's condition. This allows us to have compassion for those who are in judgment rather than being defensive towards them.
In another way, allowing more diverseness in our communities and states allows more choice and more feeling of freedom. If you want to be a KKK member, you can move to the KKK state or community for example but everyone should be free to travel to whichever community they want. Giving them the freedom for their soul to expand can help them see the light but forcing them to change usually takes much much longer if it works at all. If they commit murder or intrude on someone else's path then we take them out of society and offer them help. How is their healing gauged before we allow them back in? I don't know but I believe we can figure it out.
sex and the path to enlightenment
IMHO, the more focus we put on sex and what organs someone has the more physical we become. Is this bad? No, nothing is bad from a higher level perspective, but perhaps our choices to be overly physical are creating more suffering than we wish for through judgment, hate, and resentment. If it is our goal to become personally enlightened or an enlightened community, then being overly focused on our bodies is a form of attachment to them that will make it harder for us to ascend to higher (lighter) less physical dimensions.
Of course, ascension is actually an illusion because we are all multidimensional beings already.