How would YOU tell those caught up in transgender/Homosexual/lesbians lifestyles that what they are advocating and continue to be involved in is sexual sinning against God and themselves then?
I'd tell them for all have sinned and fall short of the glory of God.
I'd tell them that Scripture shows that God demands confession and repentance from ALL of their sin, and not just the ones that the likes of you want to focus.
I'd tell them that they should reject the condemnation coming from those who are only trying to win an argument as exampled by the lack of love that accompanies their words. And that Scripture says that those who would condemn them by leaving out God's love are just as guilty of breaking all of God's commandments as they are.
I'd then tell them about the FINISHED work of the Cross upon which Jesus Christ experienced all of the hurt and brokenness they were now experiencing. But He took it upon Himself , endured the shame and carried the Cross so that they could not be forced to believe that they still had to. And that on the third day, HE rose up in newness of life that HE extends to each and every person who asks Him for forgiveness.
YOU will never get to the point of being able to tell them that they can be forgiven.