Because it's a subject I have knowledge of and the given information is an accurate summary of some of that knowledge? Facts aren't just floating out there in

Because it's a subject I have knowledge of and the given information is an accurate summary of some of that knowledge? Facts aren't just floating out there in the aether, many of them are testable. There are also people on the internet who well tell you that vaccinations are helpful. Oh my gosh, how do you even know the truth on this crazy contraption? It's shocking that this problem of determining truth is entirely and wholly isolated to this one communications medium and no others isn't it? I guess you could always just wait for something on television to tell you the absolute truth.