Many of them are intelligent but uninformed readers of medical news. No one group or person controls the Internet, because no one owns it. The telephone company has successfully defended itself in lawsuits regarding misuse of the telephone by stating that it merely provides the lines that tie locations together but does not dictate how the phones can be used. In much the same way, the Internet is a series of high-speed data lines that tie computers together, and since each computer is independently owned, no one can dictate policies on their use. The lines are leased from telephone companies, and the same hands-off policy applies to computer lines as applies to voice lines.
Any monitoring is done individually.
The freedom of speech guaranteed to all citizens by the US Constitution is a wonderful right. And each individual can decide what to read and what to ignore, what to espouse and what to reject. This is the essence of democracy. But complete freedom also opens the door to conflict, as each of us supports the views that we hold dear. That's why we need to practice tolerance for the views of others, as difficult as that may be in some cases.