>...When people say, “I have nothing to hide.” I remind them that they have a door on their bathroom...

This was my 'go to' question for several years but it wasn't long until I met someone (we're actually now good friends) who gladly leaves the loo door open and do whatever in full view of anyone. From there I ended up with sturdier concepts, some listed below.

Another way to deal with this is to comment on their smartphone perhaps saying something like "Oh is that the new iPhone? Can I have a look" then ask them to unlock it. If they do so turn the phone away from them and start clicking on random apps or the settings and take a photos of the screen.

Also, I ask them what they earn.

Also what their debit card pin is or what their email and bank account passwords are.

I take that a step further to highlight the point:

I don’t do anything illegal in my bathroom, but damned if I want a camera in there.

I have curtains not because I feel compelled to hide, but because outsiders don't want to see what happens in my home.

the last numbers i looked at suggest 1 in 1000, would have a keenly pRurient interest.

I only use those things because of others.