If that happens, say in the loudest way possible "Dude, why the ->-bleeped-<- were you looking at me using the bathroom!?" Even if you live in a nosy community, that's pretty nasty and cannot be acceptable. So yeah, I suggest you just do what I do. If someone confronts you over what they saw or wanna know what you did bathroom-wise, turn that around on them. No one has any right to watch you do your business in the toilet (without your permission).