First of all, Stalin and Hitler clearly did not intend to "improve the quality of life for humans". They had delusions of grandiosity but they preached no utopia for ALL humanity. Maybe for their own nation as was in the case of Hitler. Besides, Hitler was a Catholic not an atheist. Remember "Gott mit Uns"?
I actually edited out the Hitler/Stalin stuff as you were responding I guess. I felt that it was a bit emtional. But since we went there Hitler was clearly not a Christian and was in fact anti Christian. But let's for the sake of argument say he did profess to be one. It is clear that he was not because of his behavior. It is not a profession of faith that makes one Christian. It is following Christ. But anyway, I was hoping that it was edited out. Oh well...
Why is an agreed upon standard of behavior not good enough? If the majority decides that it's evil to kill, rob or steal and we put in place the law enforcement systems to protect those agreed upon principles, why is a higher being necessary?
Because it is merely opinion and your opinion is no better than anyone else’s. Even if more people agree with you than me (assuming there is no standard).
How is the good vs evil argument a successful refutation of atheism?
Because it is so evident that there is such a thing. We appeal to it all the time. You have several times as cited above by Christopher. There is an absolute by which we judge these things.
For instance. A two-year-old baby being viciously murdered is always wrong. It is wrong whether or not people agree that it is or not. I think you are sensible enough to realize that the act of murdering this baby would always be the wrong thing to do. If you agree with that statement then you are recognizing something transcendent that is outside of yourself. The only other option is to say that you just "don't like it". It is only wrong because you and maybe a whole lot of other people don't like it.
Would you say that this act of murder is only wrong because it harms another? Well it may bring great pleasure to the one doing it. In order to figure out who is right or wrong in the situation where do you turn? More importantly, would it be right and moral if everyone simply agreed that it was so? (I am especially interested in you answer to that last question).
I am not trying to be emotional with the whole baby thing, sorry if it offends anyone. It just seems like a real dilemma to me. Perhaps it's somthing you have thought through already.