The laws are a pretense for action. The goal is racial fear-mongering by any means. Citizens are getting caught up in this and the administration doesn't care.
OP's comment was "why did no one stop the Nazi's". Because it didn't start with the gas chambers. It ended there. We can always make slippery slope arguments. But when that slope starts to look steep....OP's original question kind of answers itself.
People rationalize it, they downplay the atrocities, they don't care for the victims, "it's just the law", any excuse. Current citizens and illegal immigrants are thrown in overly packed cages, starved, no water, and unhygenic. I mean, how close to the gas chambers do we have to get? When they actually start stripping them of their possessions and clothes and wealth? When they start the labor camps?
OP's question is salient. Most people don't act, because it is never bad enough. It never will be. Until one day it finally is. That's why the Nazi's got so far.
Trump isn't going to gas immigrants. No, I don't think that will happen. But the slope looks steep.