Knowing first of all that Catholics look to sacred scripture and sacred tradition equally, we know that it has been the unchanging teaching of the Church that homosexual acts are sinful. If you want to back that up with scripture, I don’t know how well you have read the NT but you may have missed 1 Cor 9-10:
“Do you not know that the unjust will not inherit the kingdom of God? Do not be deceived; neither fornicators nor idolaters nor adulterers nor boy prostitutes nor sodomites nor thieves nor the greedy nor drunkards nor slanderers nor robbers will inherit the kingdom of God.”
Sodomites are those who practice homosexual acts.
Remember two things as you read this: First, all scripture is inspired by God, so think of this as Jesus’ words through Paul’s mouth. Second, you have to understand how to properly apply the scripture. It does not mean that unjust are doomed forever - it means that if they do not repent and change they bring damnation upon themselves.
The CCC beautifully lays out Church teaching on why homosexual acts and a homosexual lifestyle are sinful and against God - if you have not yet done so, read the footnotes as well:
**Chastity and homosexuality **
**2357 **Homosexuality refers to relations between men or between women who experience an exclusive or predominant sexual attraction toward persons of the same sex. It has taken a great variety of forms through the centuries and in different cultures. Its psychological genesis remains largely unexplained. Basing itself on Sacred Scripture, which presents homosexual acts as acts of grave depravity,140 tradition has always declared that "homosexual acts are intrinsically disordered."141 They are contrary to the natural law. They close the sexual act to the gift of life. They do not proceed from a genuine affective and sexual complementarity. Under no circumstances can they be approved.
**2358 **The number of men and women who have deep-seated homosexual tendencies is not negligible. This inclination, which is objectively disordered, constitutes for most of them a trial. They must be accepted with respect, compassion, and sensitivity. Every sign of unjust discrimination in their regard should be avoided. These persons are called to fulfill God’s will in their lives and, if they are Christians, to unite to the sacrifice of the Lord’s Cross the difficulties they may encounter from their condition.
**2359 **Homosexual persons are called to chastity. By the virtues of self-mastery that teach them inner freedom, at times by the support of disinterested friendship, by prayer and sacramental grace, they can and should gradually and resolutely approach Christian perfection.
Hope this helps.
