The first thing most people say when you tell them HETLAU is "prove it!"
The problem lies in what most people view as proof. In a subject matter that is complex and unfamiliar, they may be willing to accept an explanation simply because the subject matter doesn't warrant the need to have to do any research to confirm it. In other words, it is just not that important to them, so they'll take someone else's word for it.
The possibility exists the ET and UFO phenomenon resides at the other end of the spectrum in regards to the level of proof required to back up a statement like Hetlau. Even confirmation from an authority figure may be viewed as untrustworthy. In fact, if a UFO landed in plain view right in front of most people and Extra Terrestrials de-boarded the craft, they may not believe it and feel it is just some kind of elaborate hoax.
The possibility exists ET and UFOs are something that will literally have to become a commonplace everyday occurrence before most people will be willing to believe it. In other words, they can't just believe it they have to know it, essentially live it.