Hardly a diatribe, and hardly "better than you". Just explaining how, from my perspective, one possible line of reasoning about we've got to where we are, and why.
You keep bringing up things that happen in private places.
There is simply no privacy debate to be had if you're discussing what a supermarket chooses to do within the confines of its property, where you are present at the sufference of the company. Sure, I'd rather they didn't do it. But at the end of the day, they have the right to safeguard their stock (and razorblades are an incredibly popular target for shoplifters, due to the ease of disposal, high value, and small size) just as I have the right to shop elsewhere if that offends me.
In public, whilst it is polite to ask someone before taking their picture, you have absolutely no right whatsoever to this courtesy. The police and others have fallen foul of this a number of times whilst trying to prevent amateur photographers from taking pictures.
A common misconception is that a place accessible to the public, like a supermarket, is the same in law as a public place, like the street.
It's not, and rightly so.