Imagine you're a legal US resident, with a legal position in the US. You're away visiting your family in another country, and when you try to fly back home to the US, the US government won't let you back in. You could be a PhD student or a postdoc in a research lab here, living here for years, all your stuff and your friends are here - doesn't matter. Tough for you. Go home to your country, US border officials tell you.
Bullshit, right? Right. Now go sign this.
These are not American values. It has to stop.