Atheism and Ethics

[Sheldon]

Indeed, and I'd agree it is objectively harmful, but I am dubious it is objectively true that harming someone is immoral? I think that is a subjective opinion, one I share of course. Also need I point out that not everyone shares that opinion.

Well, that's good.  It's nice to have some point of agreement to build on.  So, at least descriptively, we should be able to agree that when I tell you why a thing is good or bad in this case I'm referring to facts of the matter itself.  I'm not saying "x is bad because of some fact about me" or "x is bad because of some fact about my society" - I'm saying "x is bad because of some fact about x".  We together this far?

So What I mean is that our basis for morality is subjective, I don't think it can be otherwise, for example in this instance we both think harming someone unnecessarily is wrong, we could both say why if asked, but the idea it is wrong isn't true in any objective way. As you say, once we both hold the subjective view that harming someone unnecessarily is wrong, then we can make objective assertions about actions that violate our subjective moral worldview.

Parenthetically, because we hold the subjective view harming someone unnecessarily is wrong, we would both be able to say objectively that rape is wrong, as it is an objective fact it causes lasting trauma. We could of course point out that we wouldn't want anyone harming us unnecessarily, and infer it is likely most people feel the same way, but we cannot say it is objectively wrong to harm anyone. 

I can see why this notion scares a lot of people, but there is no objective evidence to suggest that when we understand that our morality involves a subjective choice, we become any "less moral" on any level playing field.

I would far prefer the world was populated by people who questioned moral choices carefully, than people who were taught or indoctrinated to accept unquestioningly that X is wrong and Y is right. At the risk of fulfilling Godwin's law, even a "good Nazis" can blindly follow rules. The parallels between religious indoctrination are of course hard to miss, the misogyny, homophobia, racism and bigotry it has peddled as immutable truths, has cause incalculable harm, and still is. 

NB religions evolve and improve only if adherents are willing to set aside what they teach, when that conflicts with their own subjective moral worldview. It's not all bad news of course, as like other species that have evolved to live in societal groups, we have evolved to be empathetic, any species that evolved to live in societal groups would also necessarily have to know and be able to learn what were and were not acceptable behaviours to that group, it is likely the precursor to human morality we now see, which has had a leg up from us evolving a problem solving brain, and the extra time we have to examine complex moral choices, that our ancestors did not, courtesy of the agricultural and then industrial revolutions.