well there is a need to watch people
A very limited one with an established procedure, yes.
we live in complex societies where a group of jerks can do terrible things if they have enough brains to organize themselves properly.
Yes, we call them politicians. In the past their own disagreements divided them, but they're all uniting under the monied banner of Big Brother.
This does not mean we should let the 'feds' do anything they want but we possibly need a method to do it so as to enable them to look for information when need be and at the same time guarantee privacy whenever that is possible. This all can be done in relatively satisfying way as long as the 'feds' do not want to eavesdrop on all of us real time all the time which apparently is what they want. Eventually we will have to find a common ground.
We have a satisfying way that works for everyone involved. It's called getting a warrant. It begins when the police have reason to suspect that someone has committed a crime. Next, they convince a judge that these reasons are real and not bullshit fishing expeditions. Finally, the judge agrees to provide the warrant and it specifies the persons/places to be searched and the items or activities they are looking for.
The problem is, this system prevents massive surveillance and massive fishing expeditions. That's precisely why the politicians don't like it. But it's a solved problem and has been for hundreds of years now. Don't be fooled by the phoney debate and the appearance of legitimacy (of two coequal sides) it tries to create. All of this is a power grab, pure and simple. It's not necessary to protect anyone and it's not necessary to catch criminals.