I actually believe that this argument can go both ways.
Perhaps violent behavior is inherited, much like instinct is to animals. Doesn't the female black widow spider (correct me if I'm wrong-it may be another species) kill her mate for food by instinct? By law if that exact scenario was copied in our race, it would be classified as homicide, thus violence.
As a better example: if a small toddler resides in a "happy home"; both parents always home who don't curse or argue, leniency to a fair extent, nice pre-K cartoons on the TV, the child feels loved utterly, etc.; what reason is there for that child to know what violence is? (There is always error, not everything is that perfect, but again, this is hypothetical.) I'll tell you when; when the day comes that that child doesn't get his/her way. They've always known nice, and they've always gotten their way. But say that an emergency comes up, and s/he can't go to, say, the zoo on a planned date. Wouldn't s/he be disappointed? And disappointment is one thing that can and may lead to anger in the long run. Maybe they raise their voice. They don't know they're being violent, only that they're not being nice and, if the world isn't fair to them, they don't have to be fair back. Wouldn't that be the case in their mindset?
I suppose that's where there's a question between the line of "Nature" and "Nurture". What we would technically classify as violence, that hypothetical child would know nothing of. And if it is not known, being obviously not taught to them, how else would the toddler acquire it unless by inheritance?
Of course nurturing seems to be a definite cause of violence. If you're brought up in a violent community, you perceive it to be "normal", and what's normal to you, unless you're taught otherwise, commonly is perceived to be "right". That's not to say everyone who is brought up in a violent community will be violent and everyone who's not won't be, but if you put down some statistics and dig the truth out of a few stereotypes I'm sure you can put a good amount of faith on that. Violence happens in violent communities-common knowledge. (Sure, it happens in non-violent communities, too, but not as much, and when it does, it's not as severe. It's not just publicity keeping an image of a good neighborhood, it's the actual thing.)
I don't even want to bring in horoscopes and whatnot into the ordeal...but it'd be fun to see some intrigue on that matter as well. However, maybe the answer is both, maybe it is neither. I guess we'll have to look further into the subject if we're that curious, now won't we?