Because of the sorts of things Nick Redfern says here, in the first of a two-part series entitled, “Saucers of Manipulation.” Now, Nick doesn’t say the ET view is utterly impossible. He merely points to several things that those committed to an ET view seem to habitually overlook, probably since they favor some other kind of intelligence that doesn’t come from another planet.
Why Don’t “Alien” Encounters Make Sense as Extraterrestrial Contact?

Jerome Clark, showing he is a “stubborn, mule-like old geezer of Ufology,” slammed the piece
http://www.ufoupdateslist.com/2012/jul/m06-004.shtml