moral is not an absolute. everybody who claims different is either incapable of or simply refuses to see the whole picture. moral is always biased and based on socio-political goals, under guarantee not meant for every entity on the planet.
depending on the socio/political background it is just to erase individuals who do not comply with the societys goal / judification system, speaking of death penalty or in other situations disbelievers & heretics. even in non-radical ethnocultural religious systems it is justifyable to use entities who are regarded of lesser value. or - if one belongs to the wrong political faction - it is also ok and just to strip away any so called basic human rights (just call sb a terrorist and therefor a prisoner of war, and - tadaa - it is ok to do so).
guidances such as some in stone written rules are also not for the greater good, but to keep sheeps in line and not to support any outgroups.
other ideological ideas/works/concepts/books are always used to support ones own position and goals. "humanism" is just another word for a moral ethical system which puts one sentinent species above other sentinent species.
in other words any moral is as good as the other. be it based on abstract concepts, words believed to be from higher entities or taken from animal kingdom. in the end the one who sits at the non-dangerous end of a gun is the one who is right.
if you want something absolute take this:
the one thing that we learn from history, is that we do not learn from history.
If not, then obviously the normative argument of “well, lots of animals do it...” isn’t nearly morally sufficent for human behavior.