The BBFC aren't citing violence as the main reason for banning it yet it seems most of you have locked onto the violent aspect of the game as that reason (probably v.interesting from a frudien perspective).

"...unremitting bleakness and callousness of tone in an overall game context which constantly encourages visceral killing with exceptionally little alleviation or distancing..."

They are more bothered by the general tone and judging by what they have said I would reckon it's more of a danger to a kid who could or will suffer from something like depression.

To put the BBFC in context, they are a lot more liberal than they used to be, so don't knock them too much, how much stuff have they banned in recent years.