Do atheists even need an objective moral system?

[genkaus]

Yes. Nothing really stopping you from trying. Though I don't like being told how the eat so I will try to stop your efforts just like the rapist will keep on trying to rape.

(I know that sounded terrible. )

So, your position is "might makes right", then? Those in power get to dictate morality? Then that would make "power" a non-arbitrary moral value.

Perhaps for some people, a life where dissidents are not killed is a life not worth living? Or perhaps a person only values their life and hates every one else's. If said person had the magic ability to kill everyone to leave the world for himself, is that truly bad? He's merely making life "better" for himself.

Is his life better? Really? Better or worse here are not just subjective opinions - they are judgments grounded in the reality of human nature. It is not an "opinion" that a rich man with a secure future and material comforts is living a better life than a poor man living hand-to-mouth. It does not matter if one stops valuing things that make life better - their significance to life does not decrease. It doesn't matter if you don't value food - you still have to eat or your life won't be "better".

You don't choose your values in a vacuum. You don't wake up one day and arbitrarily decide on a list of things you are going to value from this point onwards. And the values you choose also have to pass the muster of objective morality. For example, you can choose to believe that a life where dissidents survive or where anyone else survives is not worth living - but those chosen values would be immoral themselves.

Science is the study of reality. People do science because they value better understanding reality. If one did not value the pursuit of understanding nature, then they would not be into science. We can call somebody a "good" or "bad" scientist based on how well they investigate reality in way that is conducive to better understanding the way reality really is.

Technological goals are ultimately arbitrary. Stopping global warming is an arbitrary goal because it's based on the value that places importance on the continued existence of mankind. But I can't see why we should ultimately care about human existence. We could just as easily say "fuck it all" and let the Earth turn into Venus.

You are missing the point entirely. I'm not talking about the moral aspects of science and technology, but using it as an analogy to it.

In this analogy, I'm equating science to morality - a certain set of concepts and principles. Technology, then, is similar to our value system - goals to be achieved by the application of those principles.

First of all, those goals cannot be chosen arbitrarily. The first test they need to pass is conformity to the principles in question. Which is why, my technological goal of turning water into wine is unscientific and my value of killing all dissidents is immoral. Secondly, even if we chose the goals arbitrarily form a set of goals that to conform, that does not make the principles to be applied subjective or arbitrary.

And if somebody does not value consistency? Perhaps for some, inconsistency (or the seeming appearence of inconsistency) is what makes a morality "legitimate"?

Irrelevant. Objective morality does not depend upon any individual's personal wishes or values. It is his values that are to judged and changed accordingly.