I get what your saying , no paint brush covers everyone. There will always be lunatics and exceptions. That said MOST people share similar definitions of right and wrong. If someones morals allow them to commit horrendous acts that's not the norm its the exception.
That's true but he makes a good point (that I think you probably agree with) in that laws provide a basic framework for societies in which people's morals differ. I don't necessarily agree with all laws, but I do my best to follow them. I may skirt or bend them so long as no one is directly hurt by my bending, depending on the situation.
I had a discussion in one of my university courses once, on how it was morally right in a certain culture to throw acid into a woman's face. By and large, the whole culture believed that was not only okay, but moral. To not believe that would have been an exception, rather than the norm that it is for many other cultures.
As you can probably see by my responses I think you raise an interest point in your thread--one that I think does need to be expanded to include more than just knives, from time to time--I'm the kind of guy who believes what is lawful isn't always right and what is right is not always lawful, so I'm not trying to say we should or shouldn't do something just because it's a law. But, as Stabman points out, it is a good framework for a society that, by and large, will have differing sets of moral values.
To get back to knives for a minute, I think a lot of people would agree that putting racist/white supremacy symbols on your knives at least borders on immoral. I know I do. But maker(s) who engage in that practice clearly have no problem with it, and let's face it, very few people actively, regularly, go against their own moral standards. One could say "I don't agree with putting such symbols on knives but it makes a profit so although I find it morally repugnant I do it anyway," but I'm inclined to think that the truth is closer to "I actually have no moral qualms about this at all." And therein lies the crux of the matter, morals are not only subjective but, one could say almost individualistic. I agree in general, most societies have a "norm" in that sliding scale, but that's not something we can count on.