It is built on the claim of Jesus Christ that He was the Son of God. Jesus unconditionally affirmed the divine origin and authority of the Old Testament in its entirety. He said He would not abrogate Moses' Law, but rather every last bit of it would be fulfilled (Matt. 5:17-18). He claimed the Law was prophetic in nature (Matt. 11:13). He built a teaching on the historical existence of Adam and Eve (Matt. 19:1-6).
This is why the LBGT claim that Jesus never talked about, or against, homosexuality is false. Jesus affirmed the five books of Moses. Because Jesus affirmed Moses in his entirety, that means Jesus affirmed each individual law contained in Moses. When Jesus endorsed Moses as a whole, He endorsed all the particular laws contained in it. Christ endorsed Moses' teachings against homosexuality.
So, whenever you debate anything about sexual morality, you are actually debating whether Jesus was God's Son, and whether He rose from the dead. If Jesus was the Son of God, then His authority is unique and absolute on matters of morality. If He wasn't the Son of God, then His was just one more voice among many.
The Christian view of sexuality is actually "worse" than most people know. Right now a battle rages over homosexuality, as if Christians oppose this only. What many people no longer seem to know is that Christianity limits every type of intercourse to heterosexual, monogamous marriage only. Every other form of intercourse is off-limits.
Heterosexual, engaged couples. Formerly-married spouses with each other. Elderly couples living together to avoid the loss of Social Security benefits. Contracts freely entered into with prostitutes. Every act of sexual intercourse outside of heterosexual, monogamous marriage is sin. This is the Christian teaching. It is incredibly rigorous, and all Christians fail it, at least in mind and often in body. But it is still the rule.
That is what I mean by calling the Christian view of sex "worse" than you might imagine. Christ taught we are not even allowed to imagine lustful thoughts about other people (Matthew 5:27-30). So, when we look at Christianity and homosexuality, we should keep it all in the context of the greater whole.
Another key factor in the Christian view of sex, which puts us at extreme odds against U.S. culture, is that none of us are gods.
We are not all-knowing, or all-powerful, or authoritative. We did not create ourselves. We have no authority to decide what is right or wrong. However, because we have become philosophically insane, we teach our children that we create our own morality. This is the way of the sociopath.
In the real world, most people realize that this idea -- that you can just make up your own morality as it suits you in the moment -- leads to violence, crime, confusion, and hypocrisy. Yet we keep on acting as if we think we are gods. We call ourselves masters of our own fate, then shout in outrage when someone else transgresses against us, or against someone we love. We call for justice for the oppressed, but by so doing we are saying that there even is such a thing as "justice", and it should not be violated.
We are hypocrites when it comes to sex. We lament the HIV-caused death of millions of young men, but we won't lament the behavior which caused their deaths. There is justice regarding everything else found in the evening news. We fight against sex trafficking and pedophilia, and we should. We fight against bullying. We oppose the selling of young girls as "brides", which still goes on covertly in some Mormon-dominated areas of the U.S. We oppose the foot-binding of women, and vaginal circumcision.
Then we claim, from out of nowhere, based on nothing, that there are no rules for sex other than consent. Where is it written that "consent" makes something right? We are not gods, not even when we consent. If Jesus Christ says something is morally wrong, who cares about our consent? It would mean we're all freely consenting to doing something that's still wrong, and for which we will pay a harsh price. Our consent is the empty howling of wind in the night.
Christianity upholds the humanity of gay people because Christianity believes in free-will, where "pop" LGBT theories deny free-will, and dehumanizes gays. If a behavior can't be criticized, taught-against, or legally prevented because the person doing the behavior was "born that way", then that is a denial of free-will. And that is a denial of human dignity.
I do not have blue eyes by choice, I was born with them. I have no free-will about the color of my eyes, and so, yes, it would be unjust to punish me for having blue eyes. If a homosexual can't be exhorted to change his or her ways because they were born that way, then that's saying the homosexual has no free-will. But then having no free-will makes them less than human. Christianity, by opposing homosexuality, reflects a high view of the humanness of gay people, because it doesn't believe they are animals or machines.
This denial of free-will, and the personal responsibility that goes with it, opens a door to all sorts of other harm. It would be wrong to criticize rage, because the angry person was born that way. It would be wrong to criticize greed, because the person was born that way. It would be wrong to criticize Obama, or Trump, or any leader, because they were all born in certain ways.
The LBGT denial of free-will (which seems to usually be an implicit or even unaware denial) leads to bad social and legal consequences. But Christianity upholds that we are people, not things. Homosexuality is an ethical behavior, and it is not an involuntary behavior. If it is involuntary, then it counts as a slavery, an addiction, and therefore it is also a self-destructive evil from which many people wish to be freed. Jesus Christ can free them.
Christians are not surprised when people say they have felt certain desires since childhood, because Christians believe that we are all born sinners. We are not born good. We are not even born as blank slates. We are born sinners, and evil feelings -- selfishness, rage, coveting -- rises up out of us spontaneously from our earliest.
Christ taught that evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander, all come from the heart (Matthew 15:19). Not from the physical part of humanity, but from the non-physical part. Of course, Christians believe we have a non-physical aspect to us, which is called our souls. Molecules don't think, feel, or make choices, yet we do all three of those things. Therefore, our reasoning, emotions, and choices come from something other than our molecules. That is the soul.
Christians do not believe human nature is good. The human soul is born fallen, dark, and cut off from God. Evil pumps up through our personalities, like the BP oil pipeline spewing raw crude out into the Gulf of Mexico. Jesus Christ can begin the process of capping it. But only Jesus Christ can cap it.
Our faith and our church opposes sexual sin. Our opposition is based on our belief in the divine sonship of Jesus Christ, and the truthfulness of the Bible. Sexual intercourse should be limited to monogamous, heterosexual marriage, which is the only God-approved form of marriage. We are not gods; we do not get to make up our own morality. Unlike race, homosexuality is a behavior and therefore a choice. We teach that human beings are made in God's image and, though born sinners, still have a degree of free-will. People are sick and dying from every kind of sexual sin, and children are suffering from this perverted, pornographic culture we have created, so we cannot stop teaching that Jesus Christ can save us from every sexual sin.