And I think you should be able to buy and sell like that - it should be your own choice.
All of the guns I own were bought from a dealer...so I’m ‘in the system’ already. And if any of my guns were ever used in a crime, the serial number would bring the police to my doorstep. So, my choice would be to use a dealer, to avoid that hassle.
Now if I bought a gun online, outside of ‘the system’, I wouldn’t be too worried about turning around and selling it online.
How many of the online sellers are in fact federal agents trying to entrap potential buyers? How many respondents to your ad are likely to be federal agents trying to entrap you into an illegal sale?