I must agree with the post that began this thread from the standpoint that attacking those who disagree with your opinion is a logical fallacy of the ad hominem abusive type. So, when Steven Hawking asks the rhetorical question why UFOs only appear to "cranks and weirdoes" (sic), he dismisses the existence of UFOs without addressing the evidence that supports it.

It seems that those in this forum, and indeed many seemingly intelligent people, are uncomfortable with those whose observations or knowledge fail to fit the officially accepted theory of things regardless of the evidence. If readers of this forum truly believe that only cranks and weirdos have witnessed UFO activity, they must believe that many air force pilots, air traffic controllers, commercial pilots, NASA astronauts and ground control employees are wackos. (Reference UFO: The Greatest Story Ever Denied)

One easy way to discredit a theory is to label it a "conspiracy theory." But let's look at the definition of that term from the Conspiracy theory entry in Wikipedia,

A conspiracy theory is a hypothesis that alleges a coordinated group are and/or were secretly working together to commit illegal or wrongful actions including hiding the existence of the group and its activities.

The unspoken statement made when labeling a position a "conspiracy theory" is that it is ridiculous and, therefore, could not possibly be true. But do you realize that over two million United States government employees and contractors hold a secret clearance? That's a lot of people secretly working together doing stuff that you know nothing about. Since you cannot know what they are doing and probably don't know who most of them are, what makes you think that there isn't one or multiple conspiracies?

Fortunately for those who plan conspiracies, people typically do not or cannot believe in them - they're too unbelievable! Hitler's conspiracy against the Jews comes to mind. Who of the non-Jewish Germans in the late 1930's actually believed that their leaders were actively wiping out millions of innocent Jews?

Anyway, forgive me for being way off topic at this point. I'm sure there is some other area for posting this kind of material and I'll be duly reprimanded.