I’ve lost count of how many times throughout the years that I’ve heard people mount a defense for gay marriage (or the non-sinfulness of homosexuality more generally) with the argument that Jesus never said anything about homosexuality. It’s an argument from silence to be sure, but the force of it (if it has any) is that Jesus could have specifically condemned homosexuality just as he did murder or adultery or any other number of sins, but didn’t. And since Jesus didn’t condemn it then it doesn’t matter if another NT author did.
One stock response is to say that Jesus doesn’t condemn every individual sin and yet even those who argue for the non-sinfulness of homosexuality or gay marriage would agree that certain things Jesus never spoke of are sins. Take child molestation as an example. Not many in the pro-gay camp would argue that Jesus would green-light pedophilia simply because he didn’t call that particular sin out by name.
Another more common response is to look at what Jesus did say and argue from the general to the particular. Jesus never said the words (so far as we know), “homosexuality is sinful and gay marriage is a sinful union,” but he did say, “I have not come to destroy the Law, but to fulfill it.” He did say that “until heaven and earth pass, not one jot or tittle will pass from the Law, until all is fulfilled.” So we would take Jesus’ general upholding of the Law and apply that to specific instances of law breaking.
But I’d take a different approach. I’d note that the person making the argument is already presupposing biblical authority. After all, they want to accept Jesus’ words as authoritative and since he didn’t specifically condemn homosexuality (in general) or gay marriage (in particular) then neither should we. But Jesus’ words are recorded in Scripture and Scripture was written by men other than Jesus. By taking Jesus’ words as authoritative you’re taking the recorder of his words as authorities.
And since the Gospel writers’ words were inspired (= breathed out) by the Holy Spirit just as the writers of the epistles’ words were, then we can’t possibly pit Paul against Jesus. Paul was no less inspired than Matthew, Mark, Luke, and John. We can’t take the clear condemnations of homosexuality in Paul and disregard them because Jesus didn’t say them. At least we can’t do that and be consistent.
If one were to do that then I’d ask why they’re appealing to Jesus at all. If they want Jesus’ words to be authoritative then Scripture has to be authoritative, But if they don’t want Scripture to be the authority then they don’t want Jesus’ words either and might as well disregard them and say that they don’t really care about what Jesus did or did not actually say.