I am trying to understand proposition 3.6 of this paper (perhaps I am in over my head):
https://arxiv.org/pdf/math/0703310.pdf
If we denote the stack $\mathcal{M}$ and its coarse moduli space as $M$ then in the first couple of lines of the proof it is written that:
"By standard limit arguments we may assume that $M$ is the spectrum of a local henselian ring $R$ with residue field $k$".
My question is: I have seen what is more or less this same line written in many proofs of different flavors of the above proposition. What are these standard limit arguments and where can I find references for them?