The issue at hand is not so much an issue of sin, it is an issue of repentance. The reason this has become an issue is that the Church as a whole has taken a lax position on sin. Now I understand ultimately Christianity is about grace, and that all who call upon the name of the Lord in brokeness and with a repentant heart will be saved. Now the homosexual community has what appears to be a legitimate beef against the profesing church as a whole, and in a sense they are correct. They ask the question: "What makes us so much different from every other nominal Church member? And why would a church exclude us from Christian service while still allowing unrepentant sinners full access?" The answer to that question in most cases is absolutely nothing! Again I restate that the sexual act between two of the same gender is not the only 'abomination' in the scriptures.
What is the homosexual to think when the unrepentant adulterer or fornicator is allowed full privelege and they are excluded. What about the one who is knowingly sinful in their business practices, why whould that man or woman have full privelege while the other does not? Is not unjust balances (unfair business) also an 'abomination'. You see until the professing church becomes a repentant church they are really in no position to exclude anyone!
This issue within mainline protestant churches be they UMC, PCUSA, ELCA, and so on, serves a major divider, but what happens is that people unite on one issue i.e. abortion, homosexuality, death penalty, and so on, but the majority of those taking are stand are in no position to take a stand. Anytime I am to take a stand on any issue of sin I must first examine myself ask the Lord to expose sin in my life that I may confess and repent. So long as I am harboring sin, and justifying it I cannot take a stand on anything.