Obviously the UFO debate has it's fringe element, with supposed contactees, New Age nutcases, not to mention the slew of fake photographs (the Gulf Breeze, FL, and Billy Meier incidents for example).
Sorry, but I've met too many reputeable people while in the military who have witnessed such craft (ranging from veteran SAC pilots flying airborne alert, to security police at missile silo's). Others have told stories that show hostile intent by these craft.
http://www.nicap.org/
Yours, Mike