What's with this WEIRD overzealous privacy protection of people that aren't citizens?

Seems like a simple solution would be to ask a person when they are arrested.  If you commit a crime, it seems fair to forfeit your tourist anonymity.  If the criminal isn't a citizen, and they aren't here on vacation with a passport, you call ICE.  Wouldn't you?  Isn't that the reason they exist?

I would expect that treatment in any country I visited.  I also wouldn't be shocked and flabbergasted if I were stopped in traffic, and they asked for my passport.  But I don't have anything to hide either.