Better minds that I have talked about the quest for purpose in the absense of faith and I choose deliberately not to endorse any particular moral goal in this piece.

But you did. You said that people should fight against the moral impulse to do good to strangers at their own expense, and strive to ignore their moral revulsion at ill-treating strangers.

selfish utilitarianism (is this really any different from hedonism?) is a good a goal as any although it's not one I personally choose as a moral end goal.

You are advocating it, but not choosing to follow it yourself?

Perhaps they said something else similar and you oversimplified their meaning?

That may or may not be so but I'm going by what leading atheists claim.

I don't believe you. Leading atheists don't say that. Perhaps they said something else similar and you oversimplified their meaning?

If there are no moral facts, why are you telling us what we should and should not do?

Overindulging in fatty, sweet, salty foods appears to be harmful; this is why one may do well to limit it. What corresponding harm do you see done by tipping waitresses that one will never see again, that would be prevented by the moral code that you advocate?

You're not explicit about it, but you appear to be advocating "selfish utilitarianism": the principle that one's personal utility is the only proper moral value, and should consider other people only as a means to one's own benefit. But as I said, having thrown out shoulds at the start, I don't see how you get them back in.

The first rule of rebasing your entire ethics system is that you never tell anyone you've rebased your entire ethics system.

For much the same reasons that you should never tell anyone you're a serial killer.

I second Yvain's recommendation for further reading.

Altruism is no longer valuable in evolutionary terms, but who cares?.

What's important to us as people isn't evolutionary value, it's satisfying personal preferences derived causally but not normatively from evolutionary value. Having money is one of those preferences. Being a nice person is another one of those preferences. If you deliberately make a choice that satisfies weaker preferences than the alternative, you're just throwing away utility for no reason.

If you haven't already, I suggest reading the Evolution Sequence, especially Alien God, Adaption-Executors, and Evolutionary Psychology, and the Metaethics Sequence

Now, if you want to make this into a reaaaallly repulsive ethical dilemma, add that true utilitarians should refuse to tip so they can donate that money to a charity that produces greater utility than the tip does.

Of the current figures who accept these premises, most espouse some form of secular humanism which argues that humans are genetically programed not to lie, murder or steal, therefore this is both the right morality & the one they practice.

This sounds wrong to me. It seems rather that humans are genetically programmed to lie, murder, and steal, and that, insofar as ethics help society function smoothly, they do so by constructing a system in which people feel inhibited about doing the "bad" things they are genetically programmed to do.

Move to France for a while. You will learn not to tip, and you won't feel bad about it.

If this fills you with immediate moral revulsion

This assumes a culturally narrow "you".

Wasn't there a post here a while back that talked about how anyone positing a confidence of 0.999 on something non-trivial was most likely to be suffering from their own cognitive biases?

my somewhat admittedly sketchy reasoning:

I go to the University of Washington where there is considerable interest in the case. Of the people who have only been marginally involved in the case, most believe that Amanda Knox is innocent. Of the people who are interested in the case, many believe she is guilty. There's an obvious hometown effect here which biases towards innocence so I'm assuming those who look into the case are taking that into account when and still reach a guilty verdict.

Therefore, I assign a 70% probability to Amanda Knox being guilty (+ or - 30%).

When you encounter a road block, you don't need to give up. You can simply emulate each other's intuitions and proceed with as a provisional argument (assuming your world view is true...).