It occurs to me that I have been using some bad assumptions. Just because bars and beer festivals have some of the same trappings (crowds of people, multiple styles of beer, lots of glasses in use) that the use of glass rinsers at both places should be motivated by the same things. NOT TRUE. In a bar, there is NEVER any concern about residue from one beer affecting the next (or residue from one customer infecting the next), because each pour is into a separate, previously cleaned and sanitized glass – even for the same customer ordering another of the same beer. The bar just wants to enhance the customer experience by cooling and wetting the glass with the glass rinser.
At a festival, there is also a desire to enhance the customer experience. In this case by removing the residue from one beer before pouring the next. The need for sanitation is ONLY because a problem was CREATED by connecting customers via common contact with the glass rinser (for those of you saying DUH!, you are right). So the solution is to remove the contact (as was noted above about “triggers”). It was a matter of seconds for me to remove the spring from the glass rinser. Likewise for removing the star shaped activation ring (mine just unscrewed). So now, the glass rinser valve is inactive, and the rinser is nothing more than a touchless up-facing spray head and a basin to catch and direct the rinse water.
A simple in-line ball valve can be used for turning it on and off, or Amazon sells a foot pedal valve for under $30. Many other hand, foot, or DIY trigger projects exist.
Thanks to everyone for their input, and getting my head straight!