The issue with governments implementing mass warrantless surveillance is not training or standards, NIST or otherwise. It should be straight-out illegal. Governments do not have "free speech" rights. As for private citizens doing it: I think there are already sufficient laws about recording people without their consent. You can hire someone to stand on a corner and watch for a specific person to walk by, but a law pr…
First off, this is not true, you definitely have some rights to privacy in public (an trivial example is using a public restroom). The law also is based on what is reasonable, and I don't think nearly everyone would think it is reasonable to expect some privacy if you walked down an alley to get away from others or went to a more secluded area. These are often explicitly why people do such things.
Second, recognize that many of these laws were written long before the average person had a camera and microphone in their pockets (not to mention high quality). The environment changed and it makes sense that our laws should change to. So even if you reject the first point these arguments about "what the law says" are still not enough to dispel concerns because we can in fact change the laws. More so, we _should_ constantly be updating laws due to our changing environments and how we learn about things as they happen.
And yeah, there's also a significant difference between a private person and a government doing these tasks. The government has a lot more power, and this does mean they require higher scrutiny and accountability even if you have complete faith in them (yes, this also means corporate entities, since the concern is power dynamics). Scale certainly has changed in the last 100, 50, 20, and even 10 years. It happened fast and no matter what side you are on, you can't ignore that things have changed and are about to change even more.