I totally see where you are coming from now, P4J, and I completely agree. I think it helps Christians to understand WHY God commands us to do the things that he does. For instance, we are called to love everyone (not just the people we get along with best) because God himself is love and causes the sun to shine on both the evil and the good. We are called to save ourselves for marriage because children (the natural result of sexual activity) are happiest when they have two parents to care for them and sex itself creates an emotional and physical bond between two people ("and the two shall become one flesh") that should not be severed (as most of us have seen in either our own lives or in others' lives, one night stands are very emotionally damaging). We are called not to lust because getting involved in worldly things (like pornography--which can easily lead one down the path of sexual addiction) takes our eyes off of God's mission for our lives and off of God's command to treat each other (bodies included) with love and respect (not objects), and, as Christ says, lusting is itself a sexual act with that person. As Christians, we are commanded by Christ to follow in his example and lead Christ-like lives (or we at least aim for that). I think it helps us as Christians guiding each other not to say "this is a sin because God said so;" although this should be enough, as most of us have found out with spirited children, "because mommy says so" is not the best way to correct misbehavior, but once a child understands that the action is against his/her own good, the child--hopefully--will choose to seek good on his/her own account and try to reform. Not every sin has an intellectual reason that we can understand, but through applying the principles and reasoning that God sets forth in other parts of the Bible, we can better understand that these are sins, too. For example, homosexuality is wrong because God created Adam and Eve to start the first family, not Adam and Adam or Eve and Eve. God, thus, feels that it is in humanity's best interest to keep marriage between only males and females. God started the world in this way, and although we cannot know the precise reason God created the first marriage in this way, we as Christians must recognize that we need to follow God's example. Maybe I'm blinded by my own shortcomings, but I don't understand how someone could be a Christian and think otherwise on these issues. I do think it is important, though, for all of us Christians to understand that we, of course, still sin every day, but the key is to become aware of our sin and earnestly seek to do good. Homosexuality is on par with gossiping (I think that all sins are equal before God)--and many Christians are unaware of the gossip coming out of their own mouths about others. Pornography and sexual addictions can be difficult for even strong Christians to overcome, but part of being a Christian is identifying those parts of your life that need to be made better and trying to act upon this no matter how many times you stumble. Because someone continues to do particular sins does not mean that they do not think they are doing wrong--perhaps they are just stumbling on the path of trying to do better. Only God can judge their hearts. If someone, however, willingly acts against the spirit of God's commands set forth in the Bible, then they, in my opinion, are doing wrong, but I have no place to judge. Like I said, only God really knows their hearts. Issues like sexual immorality, murder, lying, cheating, envy, judgment, theft, hate, idolatry--are the big sins in the 10 commandments and Christ's teachings, and are essential, in my opinion, to guard against within a Christian lifestyle. These are the things I think should be inflexible for any Christian. These are also things upon which we should be inflexible with other Christians, but in our dealings with non-Christians we would do better to show compassion and love before rebuking them. Personally, I'd really like to see someone justify sexual immorality with Scripture because I cannot imagine how (or why) anyone would do that.
The tricky issues for me come in on "gray" moral areas like: Is it immoral for a woman to wear pants (the clothes of a man)? Can women cut their hair? Can women pray without covering their heads? Can women become ministers? Can women wear makeup and jewelry? (Okay, I'm a woman, so these are the issues that spring into my mind first, but I know there are others.) My Bible is not handy at the moment, but I think that most of these injunctions are in Paul's epistles to the early churches--not commands or examples of God/Christ himself. Its issues like these that I feel historical context is necessary (I'm not trying to find a "loophole" to justify my blue-jean wearing self, but earnestly seeking God's will). I do think that there is room for flexibility here since these are not (to my knowledge--do correct me if I am wrong) direct commands of God or precedents established by him. Whether we baptize by adult immersion or sprinkle infants, or take communion with wine or grape juice, I personally don't think it is that important to God or that someone will not be allowed into heaven for doing one of these things incorrectly (if there is a correct way to begin with). We are all saved by God's grace and through our faith in Jesus Christ as our savior, and because we know and love him, we seek to live lives that will show others' Christ love and forgiveness.
In conclusion, (bless you if you read this far!) I think there are certain things upon which a Christian should be inflexible, and some issues in which flexibility is not against God's will. I don't think Christianity is always so black and white, and I pray for forgiveness if I am wrong in thinking that. I am just doing my best without hope of ever being perfect.