It is you who are operating in a hypothetical. I don't write laws in actual reality, it does not look like what I would like to be true is going to be true any time soon in actual reality, and to debate whether a thing is morally justifiable does not require cost benefit analysis to resolve in actual reality. I am in reality, come join me.
I knew it was to optimistic that you had caught on. It is not an objective truth we should use evolution for any moral or legal code. I think we can do a lot better than patterning our behavior on a cold, unintelligent, and amoral natural mechanism which does not care what is right or wrong. So even if we can establish what is true of evolution (and whatever it likely would be is contradictory, justifying inconsistent behavior) it is not true that we should adopt any behavioral pattern based upon it. The only thing we can say is what action is or is not consistent with evolution. We cannot say our behavior should be based on evolution. You can not get right, wrong, should, or justice from any natural entity or process. No matter how many objective facts you can find in it, it does not contain those.
I was talking about atheistic arguments, which if atheism is built upon them would also be incoherent. I gave you Chesterton's take on it. Here it is in full (it is worth reading, history has produced only a handful of wordsmiths like him, he is called the apostle of common sense):
There is nothing new in this atheistic dishonesty. The great GK Chesterton was, in part, converted from agnosticism by the contradictions he found in the attacks on Christianity a century ago, as he relates in the sixth chapter of his masterpiece
Orthodoxy,
As I read and re-read all the non-Christian or anti-Christian accounts of the faith... a slow and awful impression grew gradually but graphically upon my mind -- the impression that Christianity must be a most extraordinary thing. For not only (as I understood) had Christianity the most flaming vices, but it had apparently a mystical talent for combining vices which seemed inconsistent with each other. It was attacked on all sides and for all contradictory reasons. No sooner had one rationalist demonstrated that it was far too the east than another demonstrated with equal clearness that it was far too the west. No sooner had my anger died down at its angular and aggressive square-ness than I was called up again to notice and condemn its enervating and sensual roundness. Chesterton then goes on to provide some examples that he encountered while still "a complete agnostic," first one similar to our dilemma above,
I was much moved by the eloquent attack on Christianity as a thing of inhuman gloom....a thing purely pessimistic and opposed to life... that it prevented men, by morbid tears and terrors, from seeking joy and liberty in the bosom of nature. But another accusation was that it comforted men with a fictitious providence, and put them in a pink-and-white nursery.... One rationalist had hardly done calling Christianity a nightmare before another began to call it a fool's paradise. This puzzled me... Christianity could not at once be the black mask on a white world, and also the white mask on a black world. The state of Christianity could not be at once so comfortable that he was a coward to cling to it, and so uncomfortable that he was a fool to stand in it. Chesterton goes on to site another example common in his (as well as our) day, I felt a strong case against Christianity lay in the charge that there is something timid, monkish, and unmanly about all that is called "Christian," especially in its attitude towards resistance and fighting....it did seem... that there was something weak and over patient about Christian counsels... (which)... made plausible the accusation that Christianity was an attempt to make man too like a sheep.... I turned the next page in my agnostic manual, and my brain turned up-side down. Now I found that I was to hate Christianity not for fighting too little, but for fighting too much. Christianity, it seemed, was the mother of wars. Christianity had deluged the world with blood. I had got thoroughly angry with the Christian, because he never was angry. And now I was told to be angry with him because his anger had been the most huge and horrible thing in human history. After providing more examples (the whole chapter is well worth reading, as is the whole book, and well, pretty much everything the man wrote) Chesterton concludes,
It looked not so much as if Christianity was bad enough to include any vices, but rather as if any stick was good enough to beat Christianity with. What again could this astonishing thing be like which people were so anxious to contradict, that in doing so they did not mind contradicting themselves?
GK Chesterton
Which brings us back to our "new atheist" friends. Perhaps it isn't the Christian God who is inexplicably the vilest and most disgusting character to ever be dreamed up by man and simultaneously the "invisible friend" of weak minds clinging desperately to a friendly-face in a menacing and foreboding universe. Perhaps it is rather the case that any argument is still "good enough" as long as it is wielded against Christianity.
Adoro Ergo Sum: On the Willingness of Atheists to Contradict Themselves if it just Attacks the Faith