What can be asserted without evidence can be dismissed without evidence.

-- Christopher Hitchens

Accuracy was sacrificed for a pleasant parallel construction. Anything can be so asserted.

And, without supporting evidence, such assertions demonstrate nothing.

The mere fact that an assertion has been made is, in fact, evidence. For example, I will now flip a coin five times, and assert that the outcome was THHTT. I will not provide any evidence other than that assertion, but that is sufficient to conclude that your estimate of the probability that it's true should be higher than 1/2^5. Most assertions don't come with evidence provided unless you go looking for it. If nothing else, most assertions have to be unsupported because they're evidence for other things and the process has to bottom out somewhere.

Now, as a matter of policy we should encourage people to provide more evidence for their assertions wherever possible, but that is entirely separate from the questions of what is evidence, what evidence is needed, and what is demonstrated by an assertion having been made.