I would not call my generic 18650 mag light a spotlight. I think at the distances I am thinking of, the lumens from my light is little different from the dipped beam of an approaching car. I use the main beam of my car sometimes to indicate things to other road users (but generally the opposite - "you can come out").

It seems to me that while aggressive, to an extent, it is also self-defence. In order to get a flash from me ("shining a spot light in faces" does not quite frame the act) the driver will have needed to have been aggressive to the point of looking like they are about to come out. This in itself strikes me as being an aggressive act, and the flash of my light is my attempt at self-defence, since I want to stay alive.

But you are right, another way of staying alive would to ride slowly at night and be more patient, another thing that the drivers who get this treatment are not prepared to be. Is the onus upon me to non or less aggressive? I think I am happy with being less aggressive.

I could also travel in a large steel box with very powerful spotlights pointing out the front all the time. Bearing in my the size of my lights, and my lack of a steel box, I find myself to be less aggressive than the road users with whom I share the road. But I am not sure. I will have a go at looking at my mag light from a distance.

Thanks to @wphamilton for the velcro idea.I am using cable ties at the moment but I will try that.