Hokum-Balderdash Assay

In his book, now on its seventh edition, Prof. V.R. Ruggiero points out around half a dozen errors that affect the "truth or relevance" of an argument. (Such errors are to be distinguished from validity errors.) Among errors of truth/relevance is that of shifting the burden of proof. Ruggiero explains that,

This error consists of making an assertion and then demanding the opposition prove it false. This is an unreasonable demand. The person making the assertion has the burden of supporting it. Though the opposing side may accept the challenge of disproving it, they have no obligation to do so. Suppose, for example, you said to a friend, "Mermaids must exist," your friend disputed you, and you responded, "Unless you can disprove their existence, I am justified in believing in them." You shifted the burden of proof. You made the assertion about mermaids, so it was your responsibility to support it. (The Art of Thinking: A Guide to Critical and Creative Thought, Harper & Row, 1984, p. 158)

In a discussion forum earlier this year a forumer therein claimed that:

The humans on Earth are the ONLY BEINGS in the three-dimensional spaces of the Universe. And the angels and demons are ALIENS to humans. Kaya tigilan ninyo ang kaiisip kung meron aliens na kagaya ng tao sa ibang planeta dahil WALA [trans.-- So stop wondering about human-like aliens on other planets because there are none!] (all caps in the original)

When I asked for substantiation, this person angrily shot back:

why don't you and anyone else DISPROVE my assertions? That's not my problem, that's your problem. (all caps in the original)

As Ruggiero says, to ask others to disprove one's claim, particularly extraordinary claims like the above universal negative, "is an unreasonable demand." It is the individual making the claim who has the responsibility of proving/supporting his claim.