It’s true that cameras and microphones can be very tiny and cheap, and connecting them wirelessly into a network is also cheap. Yes the final result is that we’re being watched and listened to more and more.
And there’s facial recognition, and possibly voice recognition.
And our personal devices are running software that can have all sorts of bad things hidden in it.
The guy has a point.
Part of the way 5G works is with microcells (it is fast enough that distance from the cell makes a notable difference in latency, so cells are close together) which increase the number of connections by more than a factor of 10, which means that the connection to each cellular device has to be tuned by azimuth - horizontal and vertical - to aim the signal beams, and by distance to adjust the power.
Just to use its basic functionality, the 5G network will not only know which tower you are attached to, but the exact direction, elevation, and distance to the connected device, making triangulation unnecessary.