In a nutshell...
>The weak deserve death.
>Grow stronger from killing the strong.
>Keep what you kill.
And D2 reinforces that it's sacrilege because a necromancer comes up in the story and the hive see it as heresy.
The 'returning dead' will probably be tied to the Taken. My beef with Destiny is that the Taken and the Hive are allied but the Taken are blasphemy to sword logic. Now THAT'S stupid.