If morality is nothing more than an evolutionary by-product, i.e. a tool developed for the purpose of prolonging one's existence and/or facilitating reproduction, it seems to make little sense to criticise a person who loses morality if they do so for the sake of evolutionary efficiency.
I don't follow your argument.
Legs were an evolutionary adaption so humans could move about the surface of the earth. Now that we have cars should we abandon our legs?
If morality is an evolutionary adaptation, seeing that it has taken as long as language to evolve it behoves us to keep it. In fact if you take the argument from evolution seriously we don't have any choice about the matter. We have it in the same way as we have our legs or our instinct from language.
What you're arguing for is an adaptation of morality to take into account changing circumstances. Not losing it. An analogy might help, if you move to China, you may decide to lose your ability to speak English & acquire the ability to speak Chinese. But in no way have you lost your instinct for language which is the essential component of language for humans as an evolutionary acquisition. Chomsky argues for this as 'deep grammar' and being biologically determined, and hence evolutionarily determined.
There is no teleology to evolution when you talk of evolution for-itself. But this doesn't mean that teleology goes away - as is commonly & popularly thought, it affirms itself as a question at a different level and context.
For me it is by no means obvious that evolution reduces to prolonging one's existence and/or facilitating reproduction indefinitely and nothing else.
Even staying within most primitive version of darvinism, nothing excludes the possibility that survival of species may (have) reach(ed) stages when something much more elaborate than that is required to survive in the long run.
Like in complicated games such as chess - to win against increasingly strong opponents you must perform more and more elaborate calculations more and more steps ahead.
Those who claim that "Evolution" is the highest, bestest, thingy ever; should really (if possible) donate to sperm banks. That is the best way to maximize your reproductive fitness. Also, I don't think most of them have actually read a contempoary textbook on evolutionary biology.
Morality, as I understand it, begins and ends with humans. We are the arbiters on what is good, the only (currently) known effective evaluator and decider of ethical decisions.
Evolution "wants" us to put our genes in an awful lot of children. I don't particularly care to do that; why should I? I'd much rather do something fun. Discover and learn, solve challenging and novel problems.
Morality/Ethics is the big evaluation parameter for when the world is a "better place." Calling it an "end" is sort of like calling the function f(x) = x + 2 a number. Functions like that act on numbers, morality "acts" on "ends."
The end, is making the world a better place.