A fair question. Let's start with Aikido being the path of peace. Therefore it uses principles which do so. Thus applied it changes what could have been a fight, a combat, a war into something else.
Now in life just look around you and relate to your own experiences. The truth is there for you to see. How many minor arguments have you seen or had, how many minor disputes have you seen or had? How many times, if you have children, have you settled differences between them. All minor that without settlement would progress into major. So plenty of bigger troubles have always been nipped in the bud, every time this happens it's a victory for peace and common sense. Those unhandled ones turn into war. Then your left with how to handle chaos. That's the last stop.
The principles in Aikido which include for example compassion have been talked about and demonstrated by all enlightened or even just aware people including all those you mentioned, be they Mother Theresa et al. They went out and demonstrated the power of such. Then alas the majority of people don't get it but boy do they talk about it whilst doing the opposite.
For me Ueshiba left a promise in saying what he said. His promise was that these things actually work if you can get them real enough, it's up to you.
Such is my view, open to debate of course.
I think you are missing my point about the people of greatness. What they all had in common was they faced great suffering. They were in the bowels of great suffering, evil, or darkness and faced it head on. Those conditions led to their greatness.
It was more than an emotional argument between Co workers or siblings, or even a ego driven bar fight. It was long term, deeply rooted suffering that extended beyond the temporary emotion of a particular event.
I believe the original question was is violence necessary or a part of Aikido. I say it is a must to face, and deal with violence at some level in order to give Aikido its purpose or relevancy. We cannot use revisionism and rewrite history and attempt to recolor it into something we desire it to be. When we accept the path of a budoka, we accept the path that directly deals with violence. There are other paths such as becoming a nun for instance that might be better suited for people that do not desire to deal with the path of violence. However all these practices deal with suffering in some way be it violence, poverty, hatred, sickness, old age etc.