It may depend how you hide it in the game.
Example -- Bioshock has the Little Sisters which the player has the choice to 'harvest' them (kill them by tearing their guts out) , but the actual violence is covered up by a green cloud of mist and the sounds of violence are largely eliminated for the child murder going on (yes its a sorta- mutant child with glowing eyes but since it can be 'saved' as an alternative and restored to being a 'cute' child...)
That was in a game from 2007 with a sequel in 2010
SO the realization of actually doing the deed is clouded and hasnt the impact of showing it in even partial detail - easy for the player to pretend its virtually the same as walking over a powerup.
So anyway, if there is a differing 'morality' then it needs to be explained/reasoned why it exists (your example of 'offing' children actually exists (and extensively advocated) in our own world with excuses as bad as being 'inconvenient' or 'unwanted' being sufficient reason to allow it -- yes Friends thats right here in River City ....)
And yes making the object of this immoral morality inhuman or dehumanized will help (at least to get you past the censors) -- why do you think mass slaughter of zombies/nazis/mutants/terrorists doesnt seem to generate much hubbub for existing games ???
We might see it in more detail but now its some 'other' that we hardly relate to....