As a permanent resident with a pending citizenship application (who came on the visa mentioned at the end of this article), I find this incredibly alarming.
I have nothing to hide, despise terrorism and the fanatics that commit it, and wish no harm on others with different social, political, or religious views. But I'm familiar enough with history to know how badly this can end. "Papers please" had consequences, especially for groups targeted for political reasons.
Just last night I was browsing Wikipedia articles on various Presidential/political assassinations after watching an episode of the PBS Vietnam War documentary that is currently being aired. Earlier this week I tried to sign up for Snapchat and discovered an active account based out of Saudi Arabia that someone had set up using my email address (via an unverified email address I assume - thanks SnapChat). I can't read arabic so have no idea what was being shared on that platform from "my" account but based upon the images it looked critical of America.
It's not much of a leap to imagine being accused of various things based upon your browsing history or social media, especially if actions like this (http://www.npr.org/sections/thetwo-way/2017/08/15/543782396/...) become more common.
The rational part of my brain keeps screaming "This is America, it can't happen here, especially if you have nothing to hide" but I also find it difficult to ignore the historical and current warning signs.