What is Atheism?

[Nonpareil]

Suppose Joe Blow is on trial for murder. It is incumbent on the prosecution show Joe is indeed guilty. The prosecution presents as evidence a bloody garment found in Joe’s car, a witness who says he heard Joe arguing with the victim, and a gun in Joe’s apartment that matches the caliber of the bullet found in the victim’s body. At this point, the defense does not say to the jury, “See! They have no evidence!” Instead the defense must give reasons why the evidence does not support prosecution’s case.

Possibly. It may also be the case that the defense is forced to accept that the evidence supports the prosecution's case, and instead has to argue that it has not been established beyond a reasonable doubt.

In the case of this, however -

Maybe the witness isn’t reliable because of dementia. Maybe it wasn’t the same gun as the murder weapon.

- then these pieces of "evidence" have been established to not support the prosecution's case, and are, in fact, not actually evidence.

With respect to the proposition that God exists, lots of evidence has been presented.

No.

Lots of things that get called evidence have been presented. But, as is the case with "the bullet is from a different gun" example you gave above, it is not actually evidence, as it fails to support the conclusion for a variety of reasons. In the case of the appearance of design example that you give, since no one can even coherently define how a designed universe would necessarily appear different from a non-designed one, asserting that there is a "clear and obvious" appearance of design is rather nonsensical.

Being called evidence is not equivalent to being evidence. This non-evidence should still, in any constructive discussion, be accompanied with justification as to its dismissal, but the fact that a polite debate partner will explain why teleology is not evidence does not make teleology evidence.