Three questions about the way "we" think of homosexuality

I recently read an article (a couple of them, actually) about a singer/musician who formerly (almost a decade ago) had a very successful career in the "Christian music" world, and who now is in a same-sex relationship. In this believer's eyes, their sexual "preference" (such as it is) is not incompatible with their faith, which is an increasingly common assertion by those who are supportive of a homosexual lifestyle.

I'll say upfront that I disagree with that assertion; I don't believe that homosexuality, as a lifestyle, is compatible with a life of saving faith in Christ, any more than a lifestyle of adultery, idolatry, habitual lying, or any other lifestyle that presents regular, constant temptation to the believer. That is to say, I believe that homosexuals who are brought to saving faith in Christ should eventually seek to break with the ways of their sinful patterns of behavior like every Christian should, and that includes homosexual behavior.

Nevertheless, as I listen/read the ongoing discussion about homosexuality and its occasional interface with Christianity, two questions come to my mind, specifically directed at Christians:

1. Why do we always only appeal to Old Testament passages to defend our views? It seems clear to me that this direction of appeal goes nowhere with an unchurched audience (and not even with a large part of the churched audience). I believe that the Old Testament is the Word of God, is living and active, and proclaims Christ clearly and boldly. I understand the place and function of Old Testament law, and I understand the degree and limit of Christ's fulfillment of the law, and I recognize (and believe) in Calvin's "2^nd and 3^rd uses of the law" which teach that the law still functions to point out our sin and instruct believers how to live righteously. Nevertheless, I know that very few people outside of the church follow that. At the same time, the New Testament contains clear prohibition of homosexual acts (check I Corinthians 6:9, and also Romans 1, especially verses like 26-27). Why don't we go there in our defense of a view of homosexual activity as sinful?
2. Why do we persist in treating homosexuals as if their sinful lifestyle is more grievous than our own besetting sins? Not very long ago, I had a long discussion with a group of pastors, Ruling Elders, and other church leaders about how our profession of faith in Christ is the basis-- the ONLY basis-- for our membership in the church. The objection that they came up with was, "what if a practicing homosexual wants to join the church?" First of all, I think this is something of a straw man; I question whether this is a problem very many PCA congregations will ever face. Secondarily, though, I would turn the question around on them and say: would you refuse membership to someone who is morbidly obese? Or someone who works in a career that is notorious for making greed-inducing amounts of money? Or someone who habitually speaks of others in a slanderous way? All of these are "lifestyles" that are hit hard by I Corinthians 6, just like homosexuality. If someone is professing saving faith in Christ, we need to embrace them and welcome them into discipleship wherein Christ might do the sanctifying work that the rest of I Corinthians 6 speaks of.

I also have a question that I would love to ask of those who purport the assertion named above, that a homosexual lifestyle is compatible with their profession of faith in Christ:

How do you handle passages such as the I Corinthians 6 verse named above? I confess that I don't know very many homosexuals, but the ones that I do know have not been able to answer this question. The best answer I usually get is something akin to, "we are free from the law in Christ." The second-best is, "I'm no more of a hypocrite than anyone else." Both of these answers imply an acknowledgement that, if taken seriously, the Bible in some way prohibits the lifestyle and behavior that they have chosen to live in. Yet when this is pointed out and they are asked if they would agree that the Bible regards homosexuality as a sin, the answer (if there is one) is, "no."

So my question is, how do you get there? The only explanation I can think of is that the Bible is disregarded as any kind of authority. I can see how non-believing people would reach that conclusion; how about practicing homosexuals who claim to have saving faith in Christ? If the Bible is not authoritative, what is their authority? How does the one whom they profess as their Savior communicate His will to them? It seems to all go downhill toward total subjectivism from there.