5G just happens to be operated at frequencies that are/could be harmful to humans.
The millimeter wave spectrum is shared by many other services, for several years but are not called 5G.
I doubt that any 5G communications equipment could be used as a weapon.
Sure, you could build a high power microwave system that could be used that way, but not using 5G comm stuff.
If it operates in the spectrum shared with 5G but uses equipment used for long distance microwave links or radar, it's not 5G. GPS with transmitters covering about the entire surface of the Earth are many miles away GPS and other wide area coverage systems like satellite TV don't really belong in this topic.
Power density of a microwave signal depends on range to target and beam width.
Beam width of an antenna system can be calculated from very old formulas.
Antennas for higher frequencies may be many many wavelengths is size without being all that physically large.
Try it, calculate the diameter of a high power horn fed parabolic dish (pretty narrow beam) that would deliver a harmful energy density at a few hundred yards.
Amateur Radio operators have legally allowed bands near all the 5G bands. We must operate within the safety guidelines published by the FCC. The ARRL has sample calculations that are easy to follow.
Here is an article on potential harm.
Frequently asked questions about the safety of radiofrequency (RF) and microwave emissions from transmitters and facilities regulated by the FCC For further information contact the FCC's RF Safety Program at rfsafety@fcc.gov or 1-888-225-5322 Index (click on topic below)
www.fcc.gov
and the frequencies/power levels available to your Extra Class ham radio neighbor
and projects
Amateur Radio Operators in the United States have access to a large amount of microwave spectrum: 1.24–1.3 GHz 2.3–2.31 GHz 3.3–3.5 GHz 5.65–5.925 GHz 10.0–10.5 GHz 24.0–24.25 GHz 47.0–47.2 GHz 76.0–81.0 GHz 122.25–123.0 GHz 134–141 GHz 241–250 GHz All above 275.0 GHz [ 1 ] This spectrum is...
rrra.org
The highest frequency that I can currently operate on is 2.4 GHZ.
(except 5.8ghz video transmitters)
I might one day make a 1000 watt 2.4GHZ system based on a microwave oven magnetron and a feed horn. Completely legal (observing appropriate safety zones) for my license class.
Police can point microwaves at you in the 5G spectrum.
Modern radar speed guns normally operate at X, K, Ka, and (in Europe) Ku bands.
Radar guns that operate using the X band (8 to 12 GHz) frequency range are becoming less common because they produce a strong and easily detectable beam. Also, most automatic doors utilize radio waves in the X band range and can possibly affect the readings of police radar. As a result, K band (18 to 27 GHz) and Ka band (27 to 40 GHz) are most commonly used by police agencies.
For cell towers in 3G, 4g, or any of the current 5G frequency range the telecommunications companies have no business determining (conflict of interest) potential harm from towers at substantial distances from humans . That already peer reviewed data, for all available frequencies.
The only time harm from civilian equipment might be of concern is holding a cell phone close to the body. Even the cheap Chinese vhf/uhf radios should not be held close to important body parts while transmitting
Focusing on 5G, and not frequency in use is a way of creating fear.