In the United States for over the past decade, firearms have been used in less than 10% of violent offenses each year, which means that logically, at worst, "all guns are violence, but only part of the class of violence is guns."
At worst, because we also know that only a relatively miniscule fraction of the firearms in the United States are used in acts of violence. In 2009, there were 326,090 reported violent offenses committed using firearms (
http://bjs.ojp.usdoj.gov/content/pub/pdf/cv09.pdf); even if each was committed with a different weapon, this still represents only about 0.126% of the estimated 300 million firearms in private hands in this country (a number which excludes government-owned firearms). So in 2009, even in the United States,
~0.126% of guns = ~7.9% of violent offenses.
I myself own ten firearms, of which only two might conceivably have been used to commit acts of violence at some point in their existence, though in the case of only one that is really plausible. The weapon in question is a Soviet Mosin-Nagant M1891/30 rifle, manufactured at the Izhevsk arsenal in 1943, and the acts of violence in question, if any, would have most likely have been committed against agents of the Nazi German state and/or countries allied with it. (The other is a "Yugo SKS," more formally an M1959/66 type 2, which
might have been used in the Yugoslav wars of the 1990s, but judging by its condition spent most of its existence in a Territorial Defense armory in Serbia.)
And that brings me to the question of how, for the purposes of this discussion, we define "violence." I myself tend to define violence as the willful infliction of physical trauma (to a degree requiring medical attention) by one person on another, or the threat thereof, without regard to motivation (and thus the absence or presence of moral justification) for that act. Thus, I can use a firearm--or a bladed or bludgeoning implement, or any other weapon--to both offend or defend against another, and it's all violence. That's just part of my cultural frame of reference (much like, to the frustration of certain vegans, I don't have a visceral response to the word "flesh," because Dutch only has one word--
vlees--for both "meat" and "flesh").