Except all living things are inherently violent and knowing when to apply what amount of violence is part of being socially intelligent.
You can have societies be temporarily violent like how Americans slaughtered and killed Native Americans and took over the continent. The formation of the USA comes from this type of effective violence. Who would be the alphas in this case? the native americans? Or the ones that invaded? I know I'm a bit on the nose here, but this is just reality.
But I would agree with them that leadership does not require dominance.
I don't even think the concept of violence makes sense when the being causing it has sufficient cognition.
Violence is like a key on a piano. You were born with it. You can choose not to play that note, but it is always there, it is never not there.
You can choose to play great melodies without the violence note. You can choose to play melodies with the violence note. You can be forced in a corner and have no option but to hammer the violence key until the strings scream.