Although John 10:10 quoted Leviticus, he also referred to the "whole counsel of God", which includes the NT. However, I concede your point.
Now, are you aware of the sociology behind the fall of kingdoms? History concentrates on the military and economic reasons for the decline and fall of kingdoms while assigning the sociological factors to footnotes if social mores are even addressed. One of the many factors that contribute to the fall of kingdoms is a decline in morality.
Although poorly stated John 10:10's analysis concerning gay Christians is partially correct.
1st Corinthians 5:9-13
I wrote to you in my epistle not to keep company with sexually immoral people. 10 Yet I certainly did not mean with the sexually immoral people of this world, or with the covetous, or extortioners, or idolaters, since then you would need to go out of the world. 11 But now I have written to you not to keep company with anyone named a brother, who is sexually immoral, or covetous, or an idolater, or a reviler, or a drunkard, or an extortioner -- not even to eat with such a person.
12 For what have I to do with judging those also who are outside? Do you not judge those who are inside? 13 But those who are outside God judges. Therefore "put away from yourselves the evil person."
NKJV
The church is to judge its own members, which is composed of sinners since "all have sinned" and "if we say we are without sin we deceive ourselves".
As to Jesus' statement concerning judging, he admonished us to first judge ourselves, before we judge others. And if we do not then the criteria we use to judge another will be used to judge us.
Denominations can do as they please, however Scripture is clear that God will have the last word.
Revelation 21:6-8
6 And He said to me,"It is done! I am the Alpha and the Omega, the Beginning and the End. I will give of the fountain of the water of life freely to him who thirsts. 7 He who overcomes shall inherit all things, and I will be his God and he shall be My son. 8 But the cowardly, unbelieving, abominable, murderers, sexually immoral, sorcerers, idolaters, and all liars shall have their part in the lake which burns with fire and brimstone, which is the second death."
NKJV
God's definition of sexually immoral is clearly taught in His word.