You can suppress an airgun without permits. ATF doesn't care. I can make 400 fpe in complete silence and hit 300 yards out. It's not cheap to equip, but nobody can stop you from shooting once you have the proper gear.
WW2, airguns made of brass, usually by bicycle pump makers, were used by resistance fighters to kill Germans.
With a hand pump you can generate 3000+ psi and do more damage than you can imagine possible with things like wax bullets, ice bullets, ball bearings, even marbles.
Not for ownership. Only laws are restrictions in cities. The city I live in you can't shoot anything including air soft or sling shots. My guess is years of dead birds and broken windows made that happen. Hunting restrictions are based on caliber and power levels. Many states allow deer hunting with airguns. There are no restrictions on carrying an air gun anywhere I know about.
Look up the history of the Lewis and Clark airgun. https://www.youtube.com/watch?v=DofQ7DhjSqs
Never apologize to the left. It shows weakness and they will attack.