I think with Aikido or budo in general you must come to grip with the yin/yang of violence/nonviolence.
It doesn't seem so easy to define as black and white.
Aikido is both violent and nonviolent at the same time. The ability to choose between options and control or channel the action that results is what matters.
I just finished reading a good book by Thict Nhat Hahn on Anger. Highly recommend it for anyone studying aikido or interested in controlling anger. Anger (emotion) is what causes violence (action).
It is nearly impossible to avoid the emotion or feelings of anger...but it is what we do with it that matters.
I think in Aikido it is important to study and recognize the violence that is present in our technique and principles. It is really the only way we can respect it, and truly be nonviolent in action.