I would agree with the other comments here and say the best thing to do would be to vet sources. Things like 'looking through a commenter's history' or 'reading the About Us section of a news site' and 'looking at more than just the top 3 results from Google for sources'.
Teaching children about online manipulation without creating a paranoid world view subject to manipulation?
Ok, this is not going to be a well formulated question, because the concerns behind it are nebulous in my own head....