As opposed to
cannibalism which is a
taboo against eating one's own
species, "sennibalism" (as defined in a slim few sources, like the
Furre! RPG) is eating of any
sentient being, and is generally
frowned upon. So perhaps one day it would be against
social mores to eat
Everything, if
some theories come to be true.
It would be difficult to survive in Roguelike games if sennibalism, rather than cannibalism, carried a penalty--but given that some people can ascend with a truly vegan Monk character in Nethack, it might not be so bad.