Go Daz! Great report mate!!
Like ya say, violence in games is no excuse for someone to go out and do something similar.. ya gotta be a sick sod in the first place to even contemplate doing such a thing!
I love playing the GTA games!! Recently borrowed Saints Row off my nephew and that's a great game too (no GTA, but still fun).. and boy do I love slaughtering the undead freaks in Dead Rising

the katana, chainsaw are 2 of my fave weapons in that game, so sick, so fun
I played a few levels of Manhunt 1.. it wasn't as sick as it was portrayed but that could've been down to the PS2 Graphics

I watched the whole video of the deaths in Manhunt 2 and
that was sick..
yet I'm not easy to offend so I'd prolly happily play it if given the chance! I wouldn't buy it though.. not out of principle, just because it's not good enough to buy, needs to be more to a game than just killing..