I may be off base here, but I have to share anyway on this topic and registries from a conceptual level.
There are registries for many offenses, e.g. Ohio has a DUI registry, states have felony registries, etc, but they are not effective as people are finding and actually are detrimental to people (not just RCs – Registered Citizens). What is interesting is what SCOTUS determines COULD be applied to ALL registries conceptually, not just RC registries, which is in interest in here.
It is mentioned many times in an analogous manner, first they came for this group of people, then this group of people, and so on; so, if what you do on one type of registry is applicable, then it could be spread to others. Not saying it will, but conceptually, it is possible. Where does it stop then?