Why focus in on just this one sin, except for those cases where someone asks whether or not a certain sin is a sin? This question can be asked for any sin, and we are to make judgments as we live our lives as to what is and is not sin. This question must be answered by the Holy Spirit and the Holy Spirit most specifically speaks to us through Scripture. There are ample references below to show that homosexuality is a sin.
The problem is with sin, not homosexuality specifically. Sin cannot be allowed into heaven. We must all be transfigured by the renewing of our minds. If sin, whether homosexuality or lying or any other sin, must be confessed to God as sin, forgiven by God, and turned away from. When any person persists in a sin, justifies the sin, makes excuses for the sin, and refuses to be sorry for the sin, then that person is still in their sin. That person is haughty and too proud to submit to the Holy Spirit, Who would gladly deliver that person from the sin. And it doesn’t matter what the sin is, homosexuality, unmarried sex between any man or woman, suggestive talk, lying, sorcery (taking drugs), or any other sin.
Some people are born with a tendency to sin in one way and others have a tendency to sin in another way. All sin can be walked into. Some sins are to death. Murder and sexual sins are among those that are to death. Paul said that sexual sin is worse because it takes over your whole body, and it does if you continue in it. And that includes all sexual sins. They are very deadly and habit-forming. Yet, through Christ, anyone can be free from any sin. Salvation is a setting free from sin and the sinful nature. Yes, there is forgiveness for sin. That is the first act that God does through us, the act of sincere sorrow for sin and asking for forgiveness. God does this act through us as a first step of being born again. Then, He requires that we grow in Him. We grow by communing with Him, standing in His presence, listening to His voice (which becomes more clear to us over the years as we grow in Christ), seeing the vision of hope that He gives us telling us who we are in Christ, what we ought to be doing at the moment, and what is and what is not the body of Christ. This can’t just be a matter of hearing though. We must obey the voice of God. He speaks and faith comes. Faith is supernatural trust in Him that gives us access to His grace. His grace does the work. It is His grace that does the works through us and when He does His work through us, this transfigures us, not all at once, but a little at a time, from glory to glory.
With sexual sins, it is usually necessary that the person in the sin go to the elders of the church, confess the sin, and receive prayer. The laying on of hands of the elders of the church is a transferring of authority, in this case a transferring of authority over sin. If the bondage persists, which is probable, the person in bondage should go to the elders again and again until fully released. Sexual sin is terrible. It hangs on. Only the Holy Spirit can deliver from this. Repeated fasting and prayer may also be necessary.
If a person is flippant and resistant to God’s righteousness and desires to continue in sin, if they are not repentant or sorry for their sin and cooperating with the Holy Spirit to overcome it, then God can’t help them. God is not going to force His righteousness on them. The failure to cooperate with the Holy Spirit is the sin against the Holy Spirit. God can’t forgive it because it is the refusal to turn from sin and to receive forgiveness.