I left a comment about this on YouTube a few weeks ago and basically was told I don't know what I'm talking about (shocking that could happen on the internet, isn't it), but my thinking is that the nature of exposure is that you have an independent variable and a dependent variable. If you set your shutter, say, then your aperture has to be a certain thing to give you the correct exposure, you can't fidget with it. So in manual mode you are juggling two things that are not independent of each other, you can pick one or the other, then you are more or less locked in on the second setting. I'm sure there are some instances where manual is desirable, but I don't know what they'd be, beyond using it as a substitute for exposure compensation.
Hi Patrick J,
I totally get what you are describing. I come from a science background and am bound to logic. 
And once I learn what my camera, Canon 6D, is capable of and how to use, I know I will only use either Aperture or Shutter mode - depending on my goals. For ex., like you said - shutter -- for birds in flight.
As a newbie, a brand new newbie, like only 2 days in the field newbie, I can only add this:
Setting out, I do not have any preconceived notions about what is required to get a 'good' photo yet. I didn't know that I needed at a minimum shutter speed of 1/500 for stop action of a birds wing. Only when I viewed the pictures - finally -- at least a week later due to these tech issues -- could I see which pictures at what settings turned out 'good'. Having total control forces me to think about every setting (i.e., shutter, aperture, ISO, light meter) for every picture. For me having to think through each shot will get me up the learning curve more quickly. For the record, composition was not high on the priority list that day. I had hard enough time figuring out which dial scrolled which setting. LOL. The most important tool for me the first day in the field was the light meter and that was only going to give me a 'mid-tone neutral' if that's the correct term.
On the other hand, if I chose to use shutter priority, my composition would have been nicer, and I would have likely gotten a few more 'good' shots - but that wasn't really my goal believe it or not - good shots. I would have learned but I wouldn't have had to think very much. I did play around with ISO auto and manual which helped a lot -- taking that 3rd(?)variable out of the picture.
That's all I got. That's why it works for me.
So I don't think your way is wrong. Certainly not. Obviously not. Those that criticize you on youtube may just like to criticize people. It boils down to ones commitment, understanding, experiences, and how one learns. Again, I know for a fact, that I will eventually choose to have one priority setting. It's just logical. 
Thank you so much Patrick J for your thoughtful remarks.
Too funny. Waiting 2 weeks to see your photos was tough too. Amazing that darkrooms are obsolete. No more paper/chemicals/equipment/trays and black lights [A friend had a darkroom]. It was interesting to watch post production in practice. Now we can sit at our computer and do it in seconds.
