Under the ADA, it doesn't mater how large or small the business is. "Reasonable accommodations" have to be made at places open to the public. And so long as someone is not actively using Glass to record video, it's perfectly reasonable for someone whose prescription lenses include Glass functionality to be left alone in peace as he watches his movie. And yes, it is possible for someone's vision to be bad enough to bring the ADA into play; but still be adequately correctable with glasses.
Personally, I look forward with glee to the day when Glass IS build into prescription glasses, some business discriminates against them, and said business is crushed under the ADA. Unfortunately, it does increasingly look like that may be what it takes to finally slap this particular platoon in the luddite brigade down.
And all that is completely aside from the point that it's ridiculous and narcissistic for people to assume that the only reason anyone might be wearing Glass to to secretly spy in them. It has "substantial non-infringing uses", and all that.