Do I have to?? Basically, I think of morality as derived from evolutionary pressures. The implications of this are that moral choices (murder, theft, incest, etc.) are strongest (in terms of taboos, for example) for oneself and one's immediate relatives, but drop off as you get further from your immediate genetic relationships. Obviously these are predispositions and not absolutes, as fratricide and the like still exist, meaning these predispositions can be overcome by circumstances. So "protecting one's own" is the general rule of morality. However, humans are all 99.xxx% related, so in fact our moral code extends to much of the human race rather easily. After that, it is not difficult (though less typical) to extend the same principles to other species. It then becomes merely a matter of in-group/out-group differences. If you consider all humans to be related (and thus, "your own"), then you will treat them with the moral code that pressures us towards preserving immediate family. Alternatively, consider when Europeans considered Native Americans and Africans as another species, or the racist treatment of black Americans post-slavery (and pre-slavery, for that matter). If you extend your inclusiveness to other species (thus empathizing with non-human animals) then that basic moral code extends ever further. Many do not throw their net so wide, though, so morality remains localized to immediate family (and friends, and community, but often not much beyond that...thus, war, etc.) And there you have it.