Finding the appropriate response is key, in policy, as in individual action. Response to an undesirable behavior need not (and typically should not) be blunt or "zero tolerance". There are a wide range of better responses / interventions.
Policies (whether before-the-incident precautions or after-the-harm responses) can be evaluated both in terms of (a) moral intent and (b) moral outcomes. Ascertaining intent of a collective decision (often requiring some kind of voting or consensus) can be theoretically impossible and often practically impossible.
But when it comes to moral outcomes, there are warning signs that suggest an immoral policy: (i) lack of a targeted impact; (ii) poor benefit / cost ratio; (iii) disproportional response; (iv) high sensitivity (as in "sensitivity analysis") to imprecise or unknowable information; (v) serious unintended consequences; (vi) prioritizing ends over means
I'm not a moral relativist, but I think invoking moral relativism here is somewhat beside the point – even if it is true that morality is (somehow) objective, that doesn't mean every moral dispute is resolvable in practice. There are plenty of factual questions which are impossible to answer – for example, what was Julius Caesar's last meal? Most people assume there must be an objective answer to that question, but nobody alive now knows it, and odds are we never will (speculation, guesswork and imagination aside). Well, in the same way, even if it is true that moral questions have objective answers (I for one believe they do), there is no guarantee we can actually know what the answers to all of them are. Given that, it is reasonable for society to permit people with different moral views to coexist, rather than trying to force everyone to live by the same morality. Of course, there are certain moral issues on which society as a whole needs to take a side – the wrongfulness of murder, for example – but there are plenty of others on which it doesn't have to do so, and probably better not. I think, when it comes to questions of discrimination (on the basis of race/gender/etc), it is good that society does its best to prevent it in public settings (government, the education system, the workplace, public accomodations, etc), but trying to outlaw it in private is a road to totalitarianism, and that's true even if private discrimination is objectively morally wrong.
Sometimes, an act itself can be morally wrong, but trying (too hard) to stop other people from doing it may also be morally wrong. It is wrong to be rude to your family for no good reason, but it would be even more wrong if the police started arresting people for doing that.
> I suppose one can offer up an ethical system that claims to stand independently of biology. If so, I’d like to see it.
You are assuming a materialist philosophy of mind. If a person believes in (subjective) idealism (as in Berkeley or McTaggart), there is no particular reason why they should expect objective moral truth to be ultimately grounded in biological facts. Scientific theory is famously underdetermined by the evidence, [0] and I think that is true of metaphysical theory as well – there is a lack of empirical evidence to decide between materialism and idealism, and I think the widespread perception that the evidence somehow favours materialism over idealism is mainly due to the failure to take the later seriously as an intellectual option.
[0] https://plato.stanford.edu/entries/scientific-underdetermina...