I'm in favor of the Mike Tomlin philosophy of, "I want volunteers -- not captives."
So, let's make it a policy that, if you're a person who openly states that you'll leave the country if a vote or a court decision goes the other way, you can go to your local courthouse and sell you citizenship for a plane ticket to whichever country that you want and a check for six months rent for a studio apartment, and we transfer your citizenship to somebody who wants to be here.
You can still visit after making that trade; but you can never regain citizenship.