Paul told a church not to keep fellowship with one who is called a brother... followed by a long list of sins. The case in question was a man who had his father's wife. Paul calls this fornication. In Leviticus 18, uncovering one's father's nakedness, laying with a man as one does with a woman, sex with animals and various other sexual sins were sins for which God drove Gentiles out of the land. In Acts 15, the apostles wrote to the Gentiles to abstain, among other things, from fornication.
If a man has sex with another man, that is sexual immorality. Women should not have sex with women. If a man, for example, takes hormones to look more like a woman or if he gets castrated and gets his body parts altered to look like a woman, and has sex with a man, this is still a sin. Becoming a eunuch and taking hormones doesn't make it any less a sin.
If someone__who is called a brother__ will not repent, it is acceptable for a church to deliver that individual over to Satan for the destruction o fthe flesh that his spirit might be saved in the day of the Lord Jesus, not to keep company with him, or eat with him.
According to the Old Testament, it is an abomination/repulsive to the LORD for a man to dress as a woman or a woman to dress as a man, so we should definitely discourage this sort of thing.