I'd like to argue that all ethics are insane, despite how it might confirm the opinion of the religious that atheists are immoral. It just seems so many contradictions arise when analysing common morality.
Examples such as the infamous "When does a human come into being?" question prove my point that our morals ought to be revised or thrown out. Regarding haploid cells, many 16 year old boys could be commiting mass murder and a woman's monthly cycle could be reason for holding a funeral. Zygotes are widely regarded as the point which the human comes into developement, but no indication why this stage is more important than the haploids that created it. In developement of the body, fetus and infant lack cognitive ability which we characterize as human. Fetus' in the early stage even lack a nervous system. So defining potential to become as human is incorrect as there is no clear criteria for when to stop. Intellect is incorrect because infant and fetus lack intellect exept in the meager animalistic sense.
Soul, defined as the material embodiement of conciousness that remains after death, is a concept that hasn't materialized in scientific or philosophical evidence so any rational atheist cannot even consider it.
So we cannot define when the human begins, its still favourable to work together. Right? Game theory mathematically analyzes such behavior versus selfishness. In a situation where all agents in the "game" are selfish or all are helpful to one another, the game collapses immediately for the selfish ones (a classic example of pure anarchy), while the helpful sustain one another and are overall better off. Such a situation is far too idealistic given that some people are "moral" and some are "immoral" and some can be both given the situation. The flexible ones are best off, as well as immoral ones surrounded by moral sheep that are tooken advantage of. Working together is not nessasarily the best option and game theory alone cannot justify mindless empathy for others.
To add. An interesting effect shown by simulations is the behavior of segregation (individuals being empathetic to their particular group but violent to outsiders) actually being an effective strategy for success. This would explain religion and mob mentality.
Thats all i got for now, probably should develop my ideas a bit more. Now commence calling me an idiot and tearing my ideas to pieces.