Never too underestimate the power of financial persuasion. They have a decent government job with benefits, and refusal to carry out an order will be personally costly; so better to proceed with the assumption that the higher-ups know what they are doing, have considered all the angles, and have plans to deal with the eventual results.
Or… get fired an become a low-skilled unemployed person blacklisted from many opportunities.
I’ve read that some people have quit their jobs because they couldn’t do what they were being told to do.
Ironically, conditions are probably worse with the people who have a modicum of decency leaving and the people who are completely callous staying.
Remember that there are always two sides to this.
What we, as taxpayers, call expensive is a new income opportunity to those getting paid. So the same reprehensible corporations who operate ‘private prisons’ are quickly getting into the business of detention facilities under INS contract. And some of these seem to have close connections to Mr. Trump et al.
But then you have to be pretty strongly principled to give up your house and car and future meals for someone from a different country who won’t know what you did. Along with the futility of the action, considering the next person in line will likely be happy to do your job and take the pay that comes with it.