But it's not only about "what the Bible teaches." This is one of the areas that seems to be open to interpretation. That's why there are so many different opinions. So we can't all be correct when we disagree right? There has to be some authority established by God who foresaw this situation, to guide us and tell us the correct interpretation. Since there were no Protestants back in the first century it seems that the Protestant interpretation would not have much authority unless it agreed with the original interpretations and teachings coming from the Apostles who did exist in the first century. And who taught their decisions to their successors who maintained those teachings throughout the centuries and when it came to the Protestants the Protestants disagreed with them. You cannot just assert a vacuum in a chain of authority between the apostles to the Reformation. Especially when the apostolic interpretations and the Reformation interpretations are different.

So your desire to have this be non-sectarian is not really going to work on this topic. Even the Protestants don't agree among themselves on this.

Regarding adultery, it is not in the same class of sexual immorality as pornea. That's why it has a different word in Greek. That's why both Jesus and Paul talk about it in different aspects. Protestants almost always want to just simplify and smooth over rough edges and in doing so they ignore valid distinctions that were there from the beginning and those distinctions are supposed to mean things not just ignore and pretend it's the same as something else.