Whether customers are allowed in the shop is not the issue because 1. I obviously had the shop's permission to stand there and film how the windows were tinted and 2. Your statement implies that since customers aren't allowed in the shop, they can't see anything so their cars can be butchered as long as they don't see it.
I have multiple cars and yes, when it comes to a limited production $90k car that's bound to be a future classic, I should be overly concerned. What bothers me is that you dismiss my questions as stupid and continue to insist that this cutting/trimming the gasket the right technique when in fact, there are other professionals like yourself that don't engage this practice, which is not even recommended by 3M. Keep in mind that what works for you doesn't make it right if a customer objects to it.
J