To the thread title, I wanted to chime in with my impression of Stephen Miller – based on watching his TV performances, reading some of his writings and listening to TV talking heads talk about him. So… basically I don’t know him at all, so the following is nothing more than an impression, and probably unfair to him:
I see Miller as an agitator who essentially believes that you create “wins” by creating chaos and breakdown usually with bullying tactics -- and then, from the rubble you build things back as you want them to be and claim victory (whether victory is real or not). I think this is his methodology for power mongering, similar to tactics that have been utilized by autocratic regimes throughout history.
Trump (I believe) is strongly influenced by Miller's dogged ideological determination and impudence, and by his aggressive blueprint for "winning" (or his interpretations of winning). The rationale is that chaos (the means) is justified by the successful “end” (as interpreted by Miller/Trump), which usually means that he has successfully fired up and solidified the base.
Trump created chaos/unrest in order to “scare” Kim to the table in Singapore (“Little Rocket Man”; “Fire and Fury”; “Bigger Button”); Trump is creating chaos in the international marketplace (tariffs) to bully others into new "deals" that he can claim will “put America first" to the exclusion of supporting friends and longer-term world interests; Trump is creating chaos amongst “friendly” world leaders (G7 dissonance; pulling out of agreements; lauding Putin and Kim); and Trump is creating chaos at the Mexican border in order to manipulate the direction of immigration policy – ultimately solidifying the fear of “The Others” among his base --justifying "The Wall" and other hardline immigration management ideas that codify his power.
I believe Stephen Miller has that smile of the ten year old boy who has successfully teased his little sister into tears. My guess is that he loves the family separation because of the chaos and division it has created—getting everyone riled up, allowing the mouthpiece (Trump) to use his greatest skill (lying) to push the left/center into compassionate musings that Trump’s base can unify in scoffing at. Long game is that the center/left will need to address the family separation legislatively -- once again providing justification of a Miller/Trump win by “proving” that it was the left that caused the immoral policy to begin with. Miller is both dangerous and smart.
Stephen Miller has far more power than a person of his experience, moral bandwidth, and intelligence should ever have in this country. The Miller-Trump team is scary.