Re: Aikido film
I think there is a difference between a teaching and a side benefit. If you train diligently in Muay Thai, you will most likely get to be pretty fit, unless the rest of your life works against that, which is certainly possible. But it is a side effect. Muay Thai is not fitness training, it is not designed to optimize fitness of any kind. Teachers of Muay Thai may know something about fitness training, and may even choose to incorporate some of what they know into their Muay Thai classes -- but if that happens, it's a happy accident. I don't think anyone would say that someone is not qualified to teach Muay Thai if they can't expound on exercise physiology or design a workout program whose goal is optimum fitness.
I believe the relationship between aikido and spiritual development is the same. If you train diligently in aikido, you are likely to develop some skills that will also aid you if you choose to pursue the study of various spiritual traditions. One example is the skill of focus, of "being here now". In aikido we learn some form of this by trial and error, without really being taught: we struggle with a technique, we overthink it, our heads fill with thoughts like "Ugggh, why did I have to get stuck working with him? He always tries to mess me up, and I'm having such a hard time with this!" We worry about an upcoming test, and experience anxiety because we're just not getting this technique right. We feel bored and wonder what's for dinner, or start planning a meeting at work tomorrow. Eventually, we learn the hard way to find our way back to the present moment. This skill is helpful when brought to various practices such as Zen meditation, but it is not the same thing as Zen meditation. It is not a spiritual practice, it is not a spiritual discipline, and our trial-and-error acquisition of this skill does not constitute a spiritual teaching. Nor does an aikido sensei's brief moment of "meditation" before and after class constitute a spiritual teaching. An aikido sensei may practice any spiritual tradition or none at all; of those who do, few are qualified to teach it, and fewer still bring it into the dojo. And, mercifully, of the many who are not qualified to teach spiritual practices, the large majority don't have the arrogance to attempt it.
I want to add this also: the statement that aikido is not a spiritual practice does not diminish it in the least. It is what it is, it is a part of one's life, and it's a matter of opinion how life should be lived. Various spiritual traditions have strong opinions on this, of course, and if you follow one of these, that has implications for how you do your aikido, or anything else. But the what of the "how", so to speak, isn't implicit in aikido somehow, isn't uniform or omnipresent for aikido practitioners.