Nature's Laws

[Angrboda]

What dogma specifically does it get turned into?  What assertion are you claiming that (some) atheists make?

(And is what only some atheists do to be considered diagnostic of the whole category 'atheists'?)

No, I'm not saying that what only some atheists do is to be considered diagnostic of all those who call themselves atheists.  The word, "atheism" (until fairly recently) used to mean:

a :  a disbelief in the existence of deity

b :  the doctrine that there is no deity
. . . . . . . . .
I'm not sure that I understand the meaning of the second definition, but under the "old" definition, "atheism" is clearly a dogmatic belief in stark contrast with skepticism.

Which you were referring to is unclear, but even under the old definition, 'a', atheism aligns with skepticism. Skepticism is the withholding of belief until such reason is given that compels assent. The 'a' definition is just the codification of the skeptical result, namely disbelief. If that's true, it seems you are spreading a partial definition to cover a whole. Beyond that, words change over time; why are we stuck on a previous definition of the word? That's courting the genetic fallacy.