This chapter was probably necessary for Sagan to get off of his chest. His whole life has been concerned with the Cosmos and he's sent messages out into space. One program touted him for doing so in which he stated clearly that he wasn't the first one to send a message into space at all. Television broadcasts from the 40's were the first. Hawking has very real concerns when it comes to contacting aliens and I think someone quoted Hawking in here as saying that we may be confronted with the same situation as the Indians did when they met the white man.
Hawking said this in jest but his point was real. Sagan is more optimistic but he wants to make the point clear that although the message sent into space for aliens was a way to contact them, it wasn't the first. That message, from television broadcasts isn't something that can be retrieved. It's on its way out there and can't be reversed.
Aliens and UFO's are something he would be truly interested in. It has to be his fantasy. I think, based on how many people probably bombard him and the scientific community with questions and demands for answers, a necessary chapter in some respect. It feeds the need of the book for skepticism but also helps identify some obstacles to real science that are constantly thrown up by charlatans. I think he has no love for them. They serve a purpose against science and fact finding by disseminating bad information with lasting effect.
