Reasoned debate, discussion, and voting on a consensus is a whim to you?
Within the context of the greater flow of history, yes, they are just whims. They are fleeting notions that, while certainly having a massive impact on the generations under which they are prominent, remain subject to the changing norms of a restless society. We have seen this clearly enough within our own lifetimes, with age-old moral principles being toppled over in a matter of seconds (relative to the length of time to which they were adhered).
So yes, I would say that whims is an apt description of the ever-changing notions of an unprincipled society.
That is irrelevant to the point of understanding if this reference point is actually good and benefits humanity. It may or may not. You have to demonstrate that it does these things
Demonstrations of benefit are more or less inconsequential to people who have made up their minds. There’s plenty of information to demonstrate that promiscuous sexual behavior is damaging to both individuals and society. That doesn’t matter to the people engaged in those behaviors, because they want to do things their way.
People, collectively, are stupid; and no amount of demonstration of benefit will turn a group from a course its set itself on. That has been true throughout history. It’s only when the end result of those poor decisions is made manifest that people, and society, are willing to change.
As for how I came to accept the moral standpoint of Christianity, I experienced the difference it made within my own life. I saw how my life was when I lived without it, and then how my life was when i lived with it. I also saw how modern societies with and without such guiding principles operated. That was more than enough evidence to show me that the Catholic moral system has a real claim to “rightness”.