It is a difficult predicament isn’t it! I agree, suffering is very subjective. Pain may be objective, to which Sam uses the analogy of a hot stove, in which everyone with pain receptors would likely pull their hand away at the first opportunity.
However with suffering, you may have two individuals in almost identical circumstances, and depending on their mental and emotional strength, one may suffer, one may not. These are very murky waters.
On the flipside, we do need a consensus on many aspects of morality to have law and order. I.e. killing is objectively wrong. The degree to which it is wrong may be circumstantial, but it is nonetheless wrong.
A big issue is that this is actually not agreed upon in cultures like Sharia, where apostates may be killed, adulterers stoned to death etc.
Though without the fear, or respect of God, it is difficult to objectively declare certain acts as moral or immoral.
An arbitrarily picked jury seems to be our best attempt at mitigating this fact when dealing with issues of law and order, though I’m sure there’s no shortage of miscarriages of justice with this method either.