I dont think this has been brought up so far, but i think the tested mothers were unaware of the difference between 'shooter' and 'survival horror'. Even in Dead Space the difference is quite clear.
Still way to make an advert that absolutely appeals to a rebellious teenager. I was already reading up on this years Darwin Awards and this actually made me laugh harder.
EDIT-
Most of us on the internet are very desensitised to violence, gore, porn and Rule 34 porn those who arent are transitioning to that state right now, even if they dont realise it.
Mothers only skim the shallows of the net in places like Youtube, facebook, news sites and Wikipedia. They would never normally see this kind of thing.