Outline
Homosexuality is a sin like others - it is neither good nor unforgivable. The Bible also does not teach that Christians will never struggle against homosexuality as a sin.
Romans 1.26-27 states that homosexuality is immoral and unnatural.
It is possible to be a Christian who struggles with homosexual temptations. Many homosexuals who become Christians have ongoing struggles with homosexual feelings and desires. Similarly some strongly heterosexual men and women have experienced a “spark” of homosexual interest at some point in their lives. Whether or not these desires and temptations exist does not determine whether a person is a Christian. No Christian is sinless (1 John 1.8-10), all Christians have struggles with sin, and all Christians sometimes fail in those struggles (1 Corinthians 10.13). The specific sin/temptation varies between people and so this may be homosexual desires.
The struggle against sin is what differentiates a Christian’s life from a non-Christian’s life. The Christian life is a progressive journey of overcoming the “acts of the flesh” and allowing God’s Spirit to produce the “fruit of the Spirit” (Galatians 5.19-23). Christians do sin, and sometimes horribly, which sadly may make them indistinguishable from non-Christians. However, a true Christian will always repent, will always eventually return to God, and will always resume the struggle against sin. But the Bible gives no support for the idea that a person who perpetually and unrepentantly engages in sin can indeed be a Christian.
Homosexuality should not be judged differently from other sins. 1 Corinthians 6.9-10 lists sins that, if indulged in continuously, identify a person as being redeemed and not a Christian (adulterers, thieves, drunkards etc.). Often homosexuality is singled out from this list. People may presume that someone struggling with homosexual temptations is unsaved. If someone actually engages in homosexual acts then they are definitely thought to be unsaved. However, these assumptions are not made (at least not with the same emphasis) for the other listed sins: fornication (pre-marital sex), idolatry, adultery, thievery, covetousness, alcoholism, slander, and deceit. It is inconsistent to declare people guilty of pre-marital sex as “disobedient Christians” whilst declaring homosexuals to definitively be non-Christians.
A gay Christian is possible in theory, but it is a misleading label. If the phrase refers to someone struggling against homosexual desires and temptations, yes, a “gay Christian” is possible. However the description is inaccurate for such a person, since they do not desire to be gay, and are struggling against the temptations. This person is not a gay Christian, but rather a struggling Christian just as there are Christians struggling with fornication, lying and stealing. If the phrase “gay Christian” refers to a person who actively, perpetually and unrepentantly lives a homosexual lifestyle - no, it is not possible for such a person to truly be a Christian