Perhaps the reason Democrats want to protect the mentally ill is out of self-preservation. After all if you totally exclude mental health records then it would be easier for Democrats to get guns.
You don't actually have to fix a problem if you can fix the blame for a problem. It makes for reelectability if you can always appear to be working on fixing problems. Once you actually fix a problem then you have lost that issue for the next election.
Democrats love to proclaim that they are for freedom while they take away liberty.