God said it is wrong and God knows sin and that it is wrong,and God would not say it is a sin,if it was not wrong,and God can see more clearly that it is sin than we can,until we forsake sin and receive the Spirit,then we will understand how it is wrong,and it will seem detestable to us as it is to God.
God made a man to be with a woman,so to go against that is to go against how God wants His creation to behave.
But it also falls under lust of the flesh,because if God wants a man to be with a woman then there would have to be a natural attraction between a man and a woman,so for someone to go against that they would have to be following lust of the flesh.
Like the Bible says that if a man has long hair it is a shame to him,for even nature teaches that it is a shame for a man to have long hair.
Even nature teaches that it is a shame for a man to have long hair,so it is a set course that man should know not to have long hair,and to go against that would be going against something that is a set rule.
The same with a man and a woman being together,it is a set course,a natural attraction between a man and a woman,set by God,and to go against that is to go by the lust of the flesh,because it steps out of bounds of what is not defiled.
The same way that the Bible says that creation testifies that there is a God,because the invisible things of God are clearly seen by the things that are made,so the world has no excuse for not believing there is a God.
It is a set course,given by God,that creation testifies there is a God,and to not believe there is a God after observing creation,is to sin.
The Bible said after they knew God,they knew God,they did not want to believe it,but wanted to believe that things came about in a different way,like evolution.
Nobody starts out in this world believing in evolution,but it is a natural instinct to believe their is a higher intelligence out there,for it is a set course by God,as a testimony that He does exist.It is later on in life,after they knew God by creation,that they refused to believe it.
If you look before the theory of evolution came out,all nations believed there was a God,and some even said,the God of the sun,and one of the moon,and so on.They did not have the word of God,but they had the instinct to believe in a higher power because of observing creation,for it is a set course.
A man should have a natural attraction to a woman,and a woman should have a natural attraction to a man,for it is a set course,given by God,an instinct,and to go against that is to get involved in the lust of the flesh,which is sin.
The Bible says concerning the people that do not want to believe there is a God,after observing creation that testifies there is a God,if they stay on that course for a time,God will turn them to a reprobate mind,which means that God will not work with them anymore,and all they will see is fleshy ways,in which the Bible says there is no good thing that dwells in the flesh,for God gave us a choice and the flesh is our choice,so to go by the flesh is to sin.
You will read when God turns them to a reprobate mind,and all they see are the things of the flesh,God not working with them,that they are filled with all unrighteousness,and mentions that they turn homosexual as a result of only being able to see the ways of the flesh,so it proves that homosexuality is a fleshy pleasure and a sin,and they are filled with all unrighteousness and homosexuality is included in that.
But God is not a cruel God,and God gives everybody a chance to be with Him,for the Bible says what will you do in the day of visitation,so God visits everybody and touches their heart to be with Him,but what will they do,so it is a set course,that God will also visit everybody and touch their heart to be with Him,but will they do.
So there are some things set,like instinct,set by God,and to go against that would be a sin.
Homosexuality is a sin.
People without the Spirit might not understand,but if you are led by the Spirit you will understand for you will know how God labels it as sin.