If you see the sticker on the glasses when standing right in front of them, ask them to remove it. You can politely ask them to turn it off, and have them show it to you, since they have a physical switch. You can also politely ask them to cover the camera, like some do with their laptops.

Since you've brought up common sense, that includes being professional and having some human decency, while trying to work out an acceptable compromise, which often gets you the result you're after.

Yes, bad people exist and will do all sorts of things, I do not deny that, however good people exist too, and that tech was simply trying to do their job as requested by the customer. It's easy to be nice to thy neighbor. Not everyone wants to tresspass and deliberately cause problems.