Agreed.
But what we have here is the federal government planning to unilaterally declare people incompetent for the purpose of disarming them. Yes, it's not an easy process now, but it will get simpler and faster in no time.
This is not the purview of the federal government in the first place. Add to that this will end up being a bureaucratic process, not a legal one.
There are better and more localized mechanisms for dealing with this at the state & local level. Nationalizing a process like this will evolve into full fledged tyranny in no time. Always remember we are talking about people who are openly and aggressively using federal agencies to destroy political dissidents.
You are right the SS or any other Fed agency better not be the ones deciding competency. That is strictly the purview of the courts.