I think we do have perfect knowledge of Gods laws. In fact research shows we are born with that knowledge. We don't need to be educateed in knowledge to know these moral truths as they are as Psychologist Bloom says "bred to the bone" in us.
These core morals of how to treat others like Justice, Fairness, Do no Harm which relate to the Golden Rule and Christs teaching 'Do unto others as you would have them do to you" are the basis for all morals and found in 3 month olds before they are shown or taught this by family or culture. In fact it comes natural and rather than these moral Truth being indoctrinated into humans they are actively indoctrinated out of humans as they are encultured by secular beliefs aned ideologies.
The Moral Life of Babies
Yes paul is saying this is not a moral issue to go arguing about, its a ritualistic one because he says that we should actually go along with the person of weaker faith to help them. If it was about sin and immorality Paul would hardly be saying "Go ahead sin if it helps others feel more comfortable in their belief".
But when Paul talks about Gods Law written in our Hearts because even the Gentiles who never had the Law knew the Law through their conscience either condemining them or excusing them he was talking about everyone, sinners in general and how Gods law is in us and we know we have sinned through our conscience.
We are also rational beings so we can lay there at night and reason whether we are guilty or not. But deny the Truth long enough and you begin to lose that guilt and your heart becomes hardened to sin.
Like I said research shows we are born with the basics of morality which all morality stems from. But its not rocket science. basically its about doing to others what you want done to you. I think that is why it was the 2nd Greatest Commandment because all morality is about how we treat others and that knowledge even basic seems to be bred in us as a universal thing. So we already know the Truth. Its just applying that to the ever changing circumstances we grow and live in.
For example the basic moral Truth of Do unto others may be that when you neighbours kid steals your sons phone or when someone cheats on their partner. None of us want that to happen to ourselves or anyone. This is just in us and we don't need special understanding. Its when we start to rationalise and justify contrary behaviour. Like whe you claim that the affair was ok because the couples were unhappy and finding love made them finally be happy ande fulfilled. The self truth as opposed to the Truth of the matter.
Ironically even those who say its ok for individual happiness and fulfillment over breaching traditional conventions still acknowledge that harm was done and would not like that to be done to them. In some ways people reap what they sow and the same happens to them and then they really understand why what they did was perhaps not the best. In that sense people learn from experience. But the Truth was always there and known. A bit like the Prodigal Son Parable I think.
I think in the past when the Church became dogmatic and enforced Gods Law over secular society they never allowed people to learn for themselves. But over time we have learned for ourselves like in going through Wars and seeing the horror. So we made some laws called Human Rights. They aren't knee jerk reactions but carefully reasoned Truths from learning the hard way.
From that we have not only learned about our experience but also our nature to be evil. So its important that we not only hope but actively question our own thinking and motives to find the Truth. Is what we currently think is Good qactually Good but perhaps not so Good or have we fooled ourselves again. God gave us a mind to reason Truths. They are already there we just have to find them, recognise them better or perhaps admit them I believe the more we seperate ourselevs from God the more they are hard to recognise and admit.