Is Aikido violent? No. Is Aikido Technique violent? Of course. Aikido is the study of violence so that we as practitioners can better understand violence in order to properly dissapate it.
Human beings are one of the few creatures that will kill NOT out of necessity. And when we kill unnecessarily it is always fueled by some type of emotion. Ego, Greed, Vanity, power etc. Aikido is the tool which we use to understand these emotions and to keep them in check. Whether the emotions belong to us or to someone else.
A gun is a peice of metal. It has no emotion thus it cannot do violence. The designer of the gun may have had violence in mind or not (was it an AK 47 or a 3006 hunting rifle) either way it has to be used to harm to be violent.