That's too easy. Those who hold the idea of it's all the same and their just interchangeable words and it's yet to be proved etc. don't want to know.
So it's no wonder to me that so many 'think' they can understand Ueshiba for example and yet still say the above.
Not just in Aikido but in life too, it's always a source of amusement to me. You got araes of life which are the domain of spirit or spiritual well being called Religion yet generally full of experts who don't even want to know the difference. You got areas to do with mind yet full of people and experts who can't even define one or have ever seen one. A crazy old world
I think you are mistaking a metaphor for reality and looking to impose your values, nice as they are, on others.
I actually do want to know what spirit is. That's why I keep asking for concrete, useful, reliable, and dependable definitions of the term, here and elsewhere in my life. I am continually frustrated by the ubiquitous response. "You cant have evidence that it exists until you already believe it exists and act as if it exists, and already know in your heart (never in the actual thinking organ) that it is real and true and the only way, and you'll know all this without any evidence anyway, so just believe what I tell you because I have the answer and I dont need any evidence." I think that is bullshit.
Wanting to know something is the best way to fall into fantasy, self-delusion. At some point, the religious believer will make the claim that they know the mind of their god. At some point, the spiritual aikidoka will claim they know what O-sensei meant. And always in opposition to a reasonable request for useable definitions and evidence. And always with the tone of "I know something you dont know....."
At this point, the best I see is that "spirit" and "mind" are metaphors for emotion, personality, cognitive patterns. Epiphenomena of the body's functioning. Why make more of it than that?
So, let's say I stipulate to the existence of a "human spirit" for this thread. Why not recognize that it is also violent, fear-driven, domineering, awful, murderous, angry, sadistic, and even predatory? If we're discussing our spirit in order to improve or change our spirit, we'd do well to acknowledge the parts of it we think are ugly. So, I think, discussing the predatory spirit is exactly appropriate in the spirituality section.
I know I have all that "badness" in me. I know my "spirit" can be quite evil. I'm not going to get any "better" by not discussing it, or calling it a different name. Best, I think, to pull it out, lay it on the table, and say "Yup, there I am. What of it is good, what is useful, what needs to be changed to get what I want, and what is it that I really want?"