This particular concern applies to every other medium, online and off, since the 1940s, and doesn't seem to have been a major problem in practice. More broadly,

This particular concern applies to every other medium, online and off, since the 1940s, and doesn't seem to have been a major problem in practice. More broadly, law enforcement opposing criminal conspiracies has kinda always been a thing. It doesn't seem, in practice, to have caused any major problems for people who want to exchange messages or publish newsletters (physical ones, or email) about how taxes suck, or even about how some ethnicity is inherently bad.