A slight disagreement there since most of the RWNJs telegraph their views. While you and I may not know who they are or where they live, if reported, they can be tracked.
Terrorist groups such as the militias are tracked by Federal agencies. It's the lone wolves who are a problem, since they often fall to local law enforcement. This is why mass shooters often fall through the cracks.
It's not just law enforcement but the local laws such as red flag laws. Democrats want to ban guns and focus too much on that aspect. Better, IMO, to focus on the individual. Get the sick ones treatment.
Is there any doubt that many of the violent extremists on JPP are telegraphing violence against Americans? Sure, most of them are all talk, but it only takes one nutjob to commit mass murder. Are any good guys checking up on them? Probably not.