It is all a lot more fundamental than it sounds – it's a question of how knowledge accumulates in the world.
There is an unnecessary focus on details here, but they do need restating: Israel Folau is a hulking – and once much loved – Australian rugby player who takes his religious faith seriously. So serious in fact, that he is now willing to risk his career and reputation over the question of whether or not gay people are going to hell. He thinks they are, and that they can still be saved if only they repent and reform. Australian Rugby thinks differently, and so seemingly parochial questions of offense, freedoms, and contractual responsibilities are being arbitrated in strangely public ways.
This is only because – despite Karl Popper solving the issue a century ago – most people still don't understand how it is that we can know anything; how it is that knowledge develops, and with it how progress – moral or technological – is ever possible. It is not an overstatement to say that we have forgotten the most important lesson that our species could ever learn.
The details of what was said, what was breeched, who was offended, and what freedoms are protected, just don't matter when it comes to the question of what should be done about Israel Folau. The improvement in gay rights over recent decades is undoubtedly a positive, and not something that most people would want to wind back. But though the attachment to this progress is charged with heavy emotion, the only reason that it isn't reversed, is one that is cold, impersonal, and above all, explanatory.
It has always tended to lag behind technology, but moral progress is happening all around us, all the time. But that doesn't mean that the growth of moral knowledge (and knowledge in general) is linear. All theories that claim to start from a foundation are not only false, but cruel. The idea that something is known for certain, carries the imputation that questioning that certainty deserves punishment. Because only someone who is deliberately malicious dares to criticise what they know to be true.
It is unsurprising then, that for most of human history the permanent state of things has been stagnation and suppression. Every time we discover new knowledge, the next question can always be 'why that way, and not another'. A foundation doesn't allow this – and without questioning of this kind we cannot discover problems, let alone solve them. And so until the enlightenment and the scientific revolution, in the course of any given human life nothing ever really improved. The world you were born into was the world you died in; almost entirely unchanged.
For these people, the problem wasn't bad ideas – because bad ideas are the general state of things – but rather ideas about the world that discouraged change. New ways of organising political institutions, health care, marriage, or even new ways of understanding what constitutes a good life for example, weren't just dismissed as wrong, but silenced as heretical. The problem here is the issue of fundamentals – people believed that knowledge came from authorities, and that this knowledge was also self-evident.
With this bug in our thinking, a large chunk of philosophical thought was dedicated to questions of 'who should rule' or 'how do we get the best people into power'. The question itself was wrong. Instead of asking who should rule, Karl Popper turned it over and wanted instead to know 'how do we best remove bad leaders'. What he had stumbled on was an understanding that the natural state of things is error, and that the truth is never obvious. So what is needed is not authorities, but constant error-correction and a tradition of criticism – a commitment to rapid change and recursive improvement.
This doesn't mean that no one can ever say that a particular moral theory is better than another, but rather that moral progress is available to us only because no one has a claim – as they did for most of our history – to understand the future growth of knowledge. We have come a long way, and every piece of that progress was fought tooth-and-nail by people claiming to know what was always beyond them (and always an obvious tautology): tomorrow's knowledge, today.
This also applied to the advocacy of gay rights. At every step people were saying not just that homosexuality was immoral and therefore should be illegal or limited, but also that this would remain true into the future. You only have to go back fifteen or twenty years and the consensus in every country – no matter how enlightened – was against gay marriage… at a minimum. This was – at the time – as foundational a moral principle as that of murder or theft being wrong.
It was only by embracing Karl Popper, and the acceptance that no truth is so incontrovertible that it cannot be questioned, that gay rights advocates ever got a hearing, and then slowly managed to snowball those early noises into broader acceptance, and eventually social change.
The change happened by explanation. By the open challenge of one set of ideas, by a better set of ideas. People were not shamed or coerced into changing their minds, they were convinced. This is how knowledge works: most of us have this strange impression that knowledge is literally transferable, that it can be downloaded from one person to another. This is wrong in so many ways – it can't possibly exist like this. When someone changes their mind or gains some form of new knowledge, they have in fact given it to themselves – acquired only, and always, through that individual's creative engagement with it.