If 2 people (A and B) are identical (everything is identical) and A punches B for no reason, B is hurt and thinks, “A should not punch B”.
This is an ought statement that isn’t backed up by any fact and might be wrong. But B thinks, “A should not punch B”.
Now let’s say it had happened in reverse and B had punched A for no reason this is actually the identical scenario because I said the people are identical. So ApunchB=BpunchA.
If B thinks that ApunchB is wrong then B thinks that BpunchA is wrong. B might not think that BpunchA=ApunchB but that is like not believing 2+2=4. B might be wrong that ApunchB=wrong but if B thinks that ApunchB=wrong then BpunchA=wrong.
(I know the golden rule is in the bible but can be arrived at through logic).
This is the first basic building block that can be built upon starting with the belief that someone harming you against your will for no reason is wrong.
You can say what about someone who doesn’t think ApunchB is wrong (ie. they don’t think someone harming them is wrong, I think there is close to nobody that doesn’t think it is wrong for someone to harm them against their will.)
So am I saying this is morality because everybody agrees? No many people probably don’t even agree that morality is about experienced harm. But those people probably believe it is wrong for someone to just harm them because they feel like it.
So perhaps morality emerges from the knowledge of the experience of suffering and that each of us thinks and feels that it is wrong for someone to harm us against our will. This can then be built upon logically.