Humans are intelligent but I think we are violent. Violence does not have to be learned. It is an innate reaction to threats or frustration. However, acting without violence has to be learned. I think that Lord of the Flies is accurate. Put humans in a situation without rules and they will descend into violence.
Violent in comparison to what? It's relative. Humans are less violent than some species (for example, the spiders who kill and consume thier prey after mating with them!). At the same time, we are a great deal more violent than many species. For me, an important question is: how can we replace violence with more intelligent, less harmful modes of conflict resolution?
I think that we are programmed for violence as an evolutionary imperative. How can a species survive if it cannot defend itself, for example, or expand its "turf"? We also have an evolutionary imperative to cooperate, since a species cannot survive without cooperative efforts.
Thomas Hobbes in Leviathan argued that humanity naturally tends toward evil and violence:
"No arts; no letters; no society; and which is worst of all, continual fear, and danger of violent death: and the life of man, solitary, poor, nasty, brutish and short" (Chapter 12).
The mass popularity of football, action movies, boxing, horror films all seem to suggest that society thrives, even craves, violence, but I also think that the popularity of these modes of entertainment suggests that modern day society has learned to channel its need for violence into acceptable formats. We can still experience the adrenaline rush, but hopefully, nobody gets killed or maimed.
Humans are violent. Humans are also peaceful.
It's true that wars have characterized human history, but even during war most people are not fighting. Even within the armed services, many people have peaceful roles (supply, medical, counseling, etc.).
So, I'd say, yes, humans are violent. Humans are a violent species, but that is not all we are.
I don't really think there is any way to argue that the human species is not violent. We clearly have the capacity for violence. As you mention, we have many wars and we tend to commit acts of violence on the individual level as well.
However, it does not necessarily folllow that there are intelligent life forms that would be less violent than we are. Essentially all animals on Earth engage in some violence so we can at least imagine that all animals on any other worlds that might contain life would also engage in violence. But we simply can't know that, of course.
Each species have thier own nature I think. whether its animals, insects, birds or human. Violence and non-violence is depend on the nature of each species. There are many animals who are violent and there are many people who are not at all violent. So, its not the matter of HUMANS only. May be its the matter of each soul ( In deep sense). If each soul is violent at base (whether its animal insect or birds, any) it is naturaly violent at surface too.