Earlier quoted context omitted.
The last time I heard about "little green men" (other than ETs) was to describe obviously-but-unofficially Russian soldiers who invaded Crimea in 2014 and claimed to be natives who wanted Russia to annex the region. https://en.wikipedia.org/wiki/Russian_occupation_of_Crimea I guess it's now being used as pejorative against groups of vaguely military style. Like the DHS agents conducting Metro Surge.
Hmm. Do you think that kristjansson was using it just to mean state-backed thugs, or were they also claiming some Russia link? (They haven't responded, and I've been downvoted for even asking the question. I am genuinely confused. I'll admit I don't follow this all very closely, but I want to understand what the phrase means here.)
That said, I described them as such because I considered the comparison to a masked and armed force of nebulous origin and ambiguous intention apt.