Quite often people make this statement—not about something that is complex—but something that is easily understandable. If someone made a reasonable explanation of what baptism for the dead is in 1 Corinthians 15:29, we might say, “That’s interesting, but it’s just your opinion; I have a different explanation.” Neither view may matter very much, and it certainly won’t affect our ability to worship with each other.
Other issues do not afford that luxury. For example, if one person thinks instrumental music should be used in worship, and another cannot conscientiously worship in a congregation where it has been introduced, then a problem exists. The same is true concerning female leadership in the church. Some will have to leave if women are appointed to lead the church.
This principle also applies to issues of morality. The immoral person must be excluded from the fellowship, which Paul makes clear in 1 Corinthians 5 and 6. To have a man attending worship who was living with his father’s wife was unthinkable. But how many people would say, “That’s just your opinion”? The same would be true of those committing or living in fornication. Is there anything ambiguous about Hebrews 13:4? “Marriage is honorable among all, and the bed undefiled, but fornicators and adulterers God will judge.” This is not a matter of interpretation.
Paul makes it clear in 1 Corinthians 6:9-11 what various forms of sin are and that they must be repented of when one becomes a Christian. In this list of sins, he includes fornicators, idolaters, adulterers, homosexuals, and sodomites. It could not be any plainer. Yet some argue that calling homosexuality a sin is just a matter of opinion. “A person cannot help it if he is born that way.” A person “born that way” would not be able to repent, but Paul affirmed that some had.
Therefore, regardless of what the majority of people may think, homosexuality is a sin; and it makes no sense to talk of homosexual “marriage.” If two runners are disqualified from entering a race, it doesn’t matter if they get married, their disqualified status remains. Any sin, in which a person continues, disqualifies him from obeying the gospel or being a Christian. Interpretation has nothing to do with it, nor does opinion enter into it; God defines what sin is so that we all can understand what we must avoid and repent of.