No, it did not used to be that "all forums had pervasive doxxing and swatting". That has never been true. It has never been widespread. Heck, swatting as we know it today wasn't even remotely common until quite recently, and doxxing has been actively frowned on and treated as potentially criminal since, like, the 80s.
I dunno what you think you're arguing, but it's nonsense.
Doxxing and swatting has always been frowned upon, but it continues to happen regardless. So the idea that it can be curbed through social stigma and criminalization is clearly false. The technology for surveillance and publishing has only improved over time.
The difference is that murder is not prone to sybil attacks. You could literally mass-automate doxxing and swatting if you wanted to. Like imagine that you just had a bot that just scraped PII from a website, purchased phone numbers off the DN, and then used text-to-speech to call in a bomb threat. You can conduct this attack anonymously from the other side of the globe.
In order to murder someone you would physically have to visit them and try not to get killed yourself. Anyone can defend against murder, but literally no one can defend against swatting. There is literally nothing you can do to legally prevent yourself from being swatted.
I honestly don't get what you are saying here. Because you can physically do something to prevent being murdered it's sensible to have laws against murder, but because you can't physically defend against swatting we should just accept it as part of our society?
I don't think that's what you are trying to say, but I can't put together what you are.
I dunno what you think you're arguing, but it's nonsense.