Having police go to homes to forcibly disarm Americans in Hawaii is going to raise death by firearms for the police and people who are said to be too sick to have guns. 
Also no gun owner will go seek mental health if they know the police will come and take their guns.
Most mass murders in the US have not been diagnosed with serious mental health conditions.
Registering all firearms with the Federal government will stimulate the Militias and Hate groups most dire prediction to their followers; the government wants your guns so they can take away your freedom.
Add a dash of paranoia and you have your witch's brew. 
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